Method and apparatus for reproducing data and method and apparatus for recording and/or reproducing data

ABSTRACT

A method and apparatus for recording or reproducing data in which high performance encoding and a high efficiency decoding are realized to lower the decoding error rate. A magnetic recording and/or reproducing apparatus  50  includes, in a recording system, a modulation encoder  52  for modulation encoding input data in a predetermined fashion and an interleaver  53  for interleaving data supplied from the modulation encoder  52  to re-array the data sequence. The magnetic recording and/or reproducing apparatus  50  also includes, in a reproducing system, a first deinterleaver for interleaving the input data for re-arraying the data sequence so that the bit sequence of data re-arrayed by the interleaver  53  will be restored to its original bit sequence, a modulation SISO decoder for modulation decoding data supplied from the first deinterleaver and a second deinterleaver for interleaving data corresponding to a difference value between data output by the modulation SISO decoder and data output by the first deinterleaver to re-array the data sequence of the difference data.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a method and apparatus for recordingdata on a recording medium, a method and apparatus for reproducing datarecorded on a recording medium and a method and apparatus for recordingand/or reproducing data for a recording medium.

[0003] 2. Description of Related Art

[0004] As a recording medium for recording digital data, there are knowna wide variety of recording mediums of the magnetic, optical orphotomagnetic system, such as a hard disc, a so-called DVCR (digitalvideo cassette recorder) or a so-called CD (Compact Disc), DVD (digitalversatile disc) and a so-called MO (magneto-optical disc).

[0005] For recording signals on these recording mediums, physicalprocessing needs to be performed on the recording mediums, such as bycontrolling the direction of magnetization by a write head for arecording medium of the magnetic recording system, or by forming pits oflengths corresponding to signals by a stamper for a recording medium ofthe optical recording system. In this case, in order to permit amplitudecontrol of readout signals or clock reproduction on the reproducing sidereading out the signals recorded on the recording medium to operate asnormally, the signal recording side for recording signals on a recordingmedium routinely uses a system of modulation encoding the signal in apre-set manner to record the resulting modulation-coded signal.

[0006] A modulation-coder, performing this modulation coding, routinelyis fed with binary signals exempt from various limitations, and outputsbinary signals free of various limitations. These limitations on thesignals include DC free limitations which state that the numbers of “0”sand “1”s be equalized over a sufficient long length of theconcatenations of “0”s and “1”s, and the (d, k) limitations which statethat the minimum and maximum numbers of consecutive “0”s and “1”s in acode be d and k, respectively. FIG. 1 shows an input/output example in amodulation coder outputting a code satisfying the (d, k)=(2, 7)limitations. Specifically, a modulation coder 150, outputting a codesatisfying the (d, k)=(2, 7) limitation, is shown in FIG. 1, by way ofconcrete explanation of the concept of the (d, k) limitations. That is,if an input signal, free of the limitation, is input to the modulationcoder 150, outputting a code satisfying the (d, k)=(2, 7) limitation,modulation-encodes the input signal to generate and output an outputsignal in which the minimum and maximum numbers of consecutive “0”s are2 and 7, respectively.

[0007] The above example indicates that, in converting a bit string freeof a limitation is converted into another bit string subjected to alimitation, the total number of the output bits is larger than that ofthe input bits. If the total number of input bits is K and the totalnumber of output bits is N, the ratio K/N is represented as a code rateR. This code rate R serves as an index indicating the efficiency of themodulation coding. If two or more modulation coders, generating outputsignals satisfying the same limitations, are compared to one another, amodulation coder having the high code rate R is able to encode moreinput bits for a given number of output bits than one having the lowcode rate R. Stated differently, a modulation coder having a high coderate R is able to record more information on a pre-set recording mediumthan one having a low code rate R.

[0008] The modulation coding may be classified into a block codingsystem in which input bits are divided into plural blocks of pre-setlengths and output bits generated are divided into plural blocks ofpre-set lengths corresponding to the blocks of the input bits, and avariable length coding system, in which encoding units of input bits andoutput bits associated with the input bits are varied. For example, theso-called 8/9 code or the 16/17 code, routinely used for modulationcoding, belong to the block coding system, whilst the so-called (1, 7)RLL code or the (2, 7) RLL code belong to the variable length encodingsystem.

[0009] For example, in a block modulation encoding system, fed with twobits as input bits, and generating three output bits satisfying the (d,k)=(0, 2) limitations, a modulation coder has a conversion table asTable 1: TABLE 1 Example of Conversion Table input bits output bits 00011 01 101 10 111 11 110

[0010] stored in e.g., a memory, not shown. The modulation coderreferences this conversion table and finds, for each 2-bit input bits,an associated 3-bit output bits, with the output bits being issued asoutput sequentially.

[0011] On the other hand, a modulation decoder for modulating-decodingthe modulation-coded signals has a back-conversion table, as Table 2:TABLE 2 Example of Back-Conversion Table input bit decoded bits 000 01001 00 010 10 011 00 100 11 101 01 110 11 111 10

[0012] corresponding to the conversion table of Table 1, stored in e.g.,a memory, not shown. The modulation decoder references thisback-conversion table to find and sequentially output 2-bit decodedbits, associated with the 3-bit input bits.

[0013]FIG. 2 shows a typical modulation decoder 160 having at least aROM (read-only memory) 161. The modulation decoder 160 is fed with aninput address signal D161 to output the contents stored in an address ofthe ROM 161 corresponding to this input address signal D161 as ademodulated decoded signal D162. In actuality, if the input bits areback-converted into decoded bits in accordance with the back-conversiontable shown in Table 2, the contents of the decoded bits are stored inaddresses of a ROM 161 of the modulation decoder 160, corresponding tothe input bits in Table 2. The decoded bits, stored in these addresses,are read out by way of performing the back-conversion.

[0014]FIG. 3 shows a typical modulation decoder 170 at least having acombination circuit 171. The modulation decoder 170 is fed with an inputsignal D171 and executes logical operations on the input signal D171 bythe combination circuit 171 to generate a modulated decoded signal D172.In actuality, if, in performing back conversion from the input bits tothe decoded bits in accordance with the back-conversion table of Table2, the three-bit input signal D171 is represented as (a₀, a₁, a₂) and atwo-bit modulated decoded signal D172 is represented as (b₀, b₁), themodulation decoder 170 generates the output bits (b₀, b₁) by thecombination circuit 171 corresponding to the following logical equations(1):

b ₀=(a ₁&a ₂)|(a ₀&!a ₁&!a ₂)|(!a ₀&a ₁&!a ₂)

b ₁=(a ₀&!a ₁)|(!a ₀&!a ₁&!a ₂)|(a ₀&a ₁&!a ₂)  (1)

[0015] where |, & and ! indicate the logical sum, logical product andlogical negation, respectively.

[0016] If the modulation coder and the modulation decoder are applied toa magnetic recording and/or reproducing apparatus for recording and/orreproducing data on or from a recording medium in accordance with themagnetic recording system, the recording and/or reproducing apparatus isconfigured as shown in FIG. 4.

[0017] That is, the magnetic recording and/or reproducing apparatus 200,shown in FIG. 4, includes, as a recording system for recording data on arecording medium 250, an error correction encoder 201 for errorcorrection encoding input data, a modulation encoder 201, a modulationencoder 202 for modulation encoding the input data, a precoder 203 forfiltering input data for compensating its channel characteristics, awrite current driver 204 for converting respective bits of the inputdata into write current values, and a write head 205 for recording dataon the recording medium 250. The magnetic recording and/or reproducingapparatus 200 also includes, as a playback system for reproducing datarecorded on the recording medium 250, a readout head 206 for reading outdata recording on the recording medium 250, an equalizer 207 forequalizing the input data, a gain adjustment circuit 208 for adjustingthe gain of the input data, an analog/digital converter (A/D converter)209 for converting analog data into digital data, a timing generatingcircuit 210 for generating clocks, a gain adjustment control circuit 211for controlling the gain adjustment circuit 208, a viterbi decoder 212for viterbi-decoding the input bits, a modulation decoder 213 formodulation decoding the input data and an error correction decoder 214for error correction decoding the input data.

[0018] In recording data on the recording medium 250, the magneticrecording and/or reproducing apparatus 200 performs the followingoperations:

[0019] When fed with the input data D201 the magnetic recording and/orreproducing apparatus 200 applies error correction coding to the inputdata D201, by the error correction encoder 201, to generate errorcorrection encoded data D202.

[0020] The magnetic recording and/or reproducing apparatus 200modulation encodes the error correction encoded data D202 from the errorcorrection encoder 201, by the modulation encoder 202, to generatemodulation-encoded data D203, which is a string of bits subjected tolimitations.

[0021] The magnetic recording and/or reproducing apparatus 200 performsfiltering on the modulation-encoded data D203, supplied from themodulation encoder 202, by the precoder 203, in such a manner as tocompensate for the channel characteristics as from the writing of dataon the recording medium 250 up to outputting thereof at an equalizer 207in the reproducing system, to generate a precode signal D204. Forexample, if the channel has 1-D characteristics, the precoder 203performs the filtering F indicated by the following equation (2):

F=1/(1⊕D)  (2)

[0022] where ⊕ denotes exclusive-OR.

[0023] The magnetic recording and/or reproducing apparatus 200 thenconverts respective bits of the precode signal D204, as binary signalsupplied from the precoder 203, by a write current driver 204, intowrite current values Is, such as by 0→−I_(S), 1→+I_(S), to generate awrite current signal D205.

[0024] By the write head 205, the magnetic recording and/or reproducingapparatus 200 applies a magnetic write signal D206, corresponding to thewrite current signal D205 supplied from the write current driver 204, tothe recording medium 250.

[0025] By the above processing, the magnetic recording and/orreproducing apparatus 200 is able to record data on the recording medium250.

[0026] In reproducing the data recorded on the recording medium 250, themagnetic recording and/or reproducing apparatus 200 performs thefollowing processing:

[0027] First, the magnetic recording and/or reproducing apparatus 200reads out the. readout magnetization signal D207 from the recordingmedium 250 by the readout head 206 to generate a readout current signalD208 conforming to this readout magnetization signal D207.

[0028] The magnetic recording and/or reproducing apparatus 200 thenequalizes the readout current signal D208, supplied from the readouthead 206, by the equalizer 207, so that the channel response since datawriting on the recording medium 250 in the recording system untiloutputting thereof at the equalizer 207 will be of pre-setcharacteristics, such as 1-D, to generate an equalized signal D209.

[0029] The magnetic recording and/or reproducing apparatus 200 thenadjusts the gain of the equalized signal D209, supplied from theequalizer 207, by the gain adjustment circuit 208, based on a gainadjustment control signal D213 from the gain adjustment control circuit211, to generate a gain adjustment signal D210. Meanwhile, the gainadjustment control signal D213 is generated by the gain adjustmentcontrol circuit 211, based on the digital channel signal D211, as laterexplained. Specifically, the gain adjustment control signal D213 is acontrol signal for maintaining the amplitude of the equalization signalD209 at an expected value.

[0030] By the A/D converter 209, the magnetic recording and/orreproducing apparatus 200 digitizes the gain adjustment signal D210,supplied from the gain adjustment circuit 208, to generate the digitalchannel signal D211. Meanwhile, the A/D converter 209 performs samplingbased on the clock signal D212 generated and supplied by the timinggenerating circuit 210. The timing generating circuit 210, fed with thedigital channel signal D211, generates clocks to produce clock signalsD212 which are output to the A/D converter 209.

[0031] The magnetic recording and/or reproducing apparatus 200 feeds thedigital channel signal D211, supplied from the A/D converter 209, to theviterbi decoder 212, which then performs viterbi decoding on the channelresponse from the upstream side of the precoder 203 in the recordingsystem up to the outputting at the equalizer 207 in the reproducingsystem, for example, the channel response R_(ch) represented by thefollowing equation (3):

R _(ch)=(1-D)/(1⊕D)  (3)

[0032] where ⊕ denotes Exclusive-OR.

[0033] The magnetic recording and/or reproducing apparatus 200 thenapplies modulation decoding on the viterbi decoded signal D214, suppliedfrom the modulation decoder 213, to realize data correspondence reversedfrom that in the modulation encoder 202 in the recording system togenerate a modulated decoded signal D215 which is an original input datastring not subjected to limitations.

[0034] The magnetic recording and/or reproducing apparatus 200 decodesthe error correction codes of the modulated decoded signal D215,supplied from the modulation decoder 213, by the error correctiondecoder 214, to generate output data D216.

[0035] By the above processing, the magnetic recording and/orreproducing apparatus 200 is able to reproduce the data recorded on therecording medium 250.

[0036] Meanwhile, in the above-described conventional magnetic recordingand/or reproducing apparatus 200, the modulation decoder 213 has no morethan the function of realizing the correspondence between binary signalsreversed from that obtained on modulation encoding by the modulationencoder 202, while the signals in both the input and the output of themodulation decoder 213 needs to be binary signals, with the result thatthe signals on the downstream side of the viterbi decoder 212 are allbinary signals.

[0037] In other words, it is necessary in the magnetic recording and/orreproducing apparatus 200 to generate binary signals on the upstreamside of the modulation decoder 213 and to process the binary signalseven on the downstream side of the modulation decoder 213.

[0038] Thus, in the magnetic recording and/or reproducing apparatus 200,in which bi-level binary signals need to be used, the information volumein the signal is diminished intentionally with the result that efficientdecoding cannot be realized to deteriorate the decoding error rate.

SUMMARY OF THE INVENTION

[0039] It is therefore an object of the present invention to provide amethod and apparatus for recording data in which high performanceencoding may be carried out to cause the reproducing system to performhighly efficient decoding operation to lower the decoding error ratesignificantly.

[0040] It is another object of the present invention to provide a datareproducing method and apparatus for performing efficient decoding tolower the decoding error rate.

[0041] It is yet another object of the present invention to provide adata recording and reproducing method and apparatus for realizing highperformance encoding and high efficiency decoding to lower the decodingerror rate.

[0042] In one aspect, the present invention provides a data recordingapparatus for recording data on a recording medium, including modulationencoding means for applying predetermined modulation encoding to inputdata, and interleaving means for interleaving data supplied from themodulation encoding means for re-arraying the data sequence.

[0043] In the data recording apparatus, according to the presentinvention, data supplied from the modulation encoding means isinterleaved by the interleaving means for re-arraying the data sequence,thereby realizing high performance encoding.

[0044] In another aspect, the present invention provides a datarecording method for recording data on a recording medium, including amodulation encoding step of applying predetermined modulation encodingto input data, and a interleaving step of interleaving data suppliedfrom the modulation encoding step for re-arraying the data sequence.

[0045] In the data recording method, according to the present invention,data supplied from the modulation encoding step is interleaved in theinterleaving step for re-arraying the data sequence for realizing highperformance encoding.

[0046] In another aspect, the present invention provides a datareproducing apparatus for reproducing data recorded by a recordingequipment for recording data on a recording medium, including modulationencoding means for applying predetermined modulation encoding to inputdata and first interleaving means for interleaving data supplied fromthe modulation encoding means for re-arraying the data sequence, inwhich the data reproduction apparatus includes deinterleaving means forinterleaving the input data in its sequence such as to restore thesequence of data bits re-arrayed by the first interleaving means to thebit sequence of the data as encoded by the modulation encoding means,modulation decoding means for modulation decoding the data supplied fromthe deinterleaving means, and second interleaving means for interleavingdata corresponding to a difference between data output by the modulationdecoding means and data output by the deinterleaving means based on thesame interleaving position information as that of the first interleavingmeans for re-arraying the sequence of the difference data.

[0047] In such data reproducing apparatus, according to the presentinvention, the data re-arrayed in its sequence interleaved by thedeinterleaving means is modulation decoded by the modulation decodingmeans, whilst data corresponding to the difference between data outputby the modulation decoding means and data output by the deinterleavingmeans is interleaved by the second interleaving means for re-arrayingthe sequence of the different data, whereby efficient decoding can berealized by exploiting the soft information for the entire decodingprocessing to lower the decoding error rate appreciably.

[0048] In still another aspect, the present invention provides a datareproducing method for reproducing data recorded by a recording methodfor recording data on a recording medium, including a modulationencoding step for applying predetermined modulation encoding to inputdata and a first interleaving step of interleaving data encoded in themodulation encoding step for re-arraying the data sequence, in which thedata reproduction method includes a deinterleaving step of interleavingthe input data in its sequence such as to restore the sequence of databits re-arrayed by the first interleaving step to the bit sequence ofthe data as encoded by the modulation encoding step, a modulationdecoding step of modulation decoding the data supplied from thedeinterleaving step and a second interleaving step of interleaving datacorresponding to a difference between data decoded in the modulationdecoding step and data re-arrayed in the deinterleaving step based onthe same interleaving position information as that of the firstinterleaving step for re-arraying the sequence of the difference data.

[0049] In such data reproducing method, according to the presentinvention, the data re-arrayed in its sequence interleaved by thedeinterleaving means is modulation decoded in the modulation decodingstep, whilst data corresponding to the difference between data output bythe modulation decoding step and data output by the deinterleaving stepis interleaved by the second interleaving step for re-arraying thesequence of the different data, whereby efficient decoding can berealized by exploiting the soft information for the entire decodingprocessing to lower the decoding error rate appreciably.

[0050] In still another aspect, the present invention provides a datarecording and reproducing apparatus for recording and reproducing datafor a recording medium, in which the apparatus includes, as a recordingsystem for recording data on the recording medium, modulation encodingmeans for applying predetermined modulation encoding to input data, andfirst interleaving means for interleaving data supplied from themodulation encoding means for re-arraying the data sequence, and inwhich the apparatus also includes, as a reproducing system forreproducing data recorded on the recording medium, deinterleaving meansfor interleaving the input data in its sequence such as to restore thesequence of data bits re-arrayed by the first interleaving means to thebit sequence of the data as encoded by the modulation encoding means,modulation decoding means for modulation decoding the data supplied fromthe deinterleaving means, and second interleaving means for interleavingdata corresponding to a difference between data output by the modulationdecoding means and data output by the deinterleaving means based on thesame interleaving position information as that of the first interleavingmeans for re-arraying the sequence of the difference data.

[0051] In the data recording and reproducing apparatus, according to thepresent invention, if data is to be recorded on a recording medium, thedata supplied from the modulation encoding means is interleaved by firstinterleaving means to re-array the data sequence, whereas, if datarecorded on the recording medium is to be reproduced, data given as adifference between second interleaving means for interleaving datacorresponding to a difference between data output by the modulationdecoding means and data output by the deinterleaving means based on thesame interleaving position information as that of said firstinterleaving means is interleaved and re-arrayed, so that highperformance encoding may be achieved, at the same time as efficientdecoding may be achieved by exploiting the soft information for theentire decoding for the code, thus significantly lowering the decodingerror rate.

[0052] In yet another aspect, the present invention provides a datarecording and reproducing method for recording and reproducing data fora recording medium, in which the method includes, as a recording systemfor recording data on the recording medium, a modulation encoding stepfor applying predetermined modulation encoding to input data, and afirst interleaving step for interleaving data supplied from themodulation encoding step for re-arraying the data sequence, and in whichthe method also includes, as a reproducing system for reproducing datarecorded on the recording medium, a deinterleaving step for interleavingthe input data in its sequence such as to restore the sequence of databits re-arrayed by the first interleaving step to the bit sequence ofthe data as encoded by the modulation encoding step, a modulationdecoding step for modulation decoding the data supplied from thedeinterleaving step, and a second interleaving step for interleavingdata corresponding to a difference between data decoded in themodulation decoding step and data re-arrayed in the deinterleaving stepbased on the same interleaving position information as that of the firstinterleaving step for re-arraying the sequence of the difference data.

[0053] In the data recording and reproducing method, according to thepresent invention, if data is to be recorded on a recording medium, thedata supplied from the modulation encoding step is interleaved by thefirst interleaving step to re-array the data sequence, whereas, if datarecorded on the recording medium is to be reproduced, data given as adifference between second interleaving means for interleaving datacorresponding to a difference between data output by the modulationdecoding means and data output by the deinterleaving means based on thesame interleaving position information as that of said firstinterleaving means is interleaved and re-arrayed, so that highperformance encoding may be achieved, at the same time as efficientdecoding may be achieved by exploiting the soft information for theentire decoding for the code, thus significantly lowering the decodingerror rate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0054]FIG. 1 illustrates an input/output example of a conventionalmodulation encoder.

[0055]FIG. 2 is a block diagram showing the structure of a conventionalmodulation decoder.

[0056]FIG. 3 is a block diagram showing the structure of anotherconventional modulation decoder.

[0057]FIG. 4 is a block diagram showing the structure of a conventionalmagnetic recording and/or reproducing apparatus.

[0058]FIG. 5 illustrates an input/output example in an interleaverapplied to a recording system of a magnetic recording and/or reproducingapparatus shown as a first embodiment of the present invention.

[0059]FIG. 6 illustrates the operation of an interleaver used in arecording system of the magnetic recording and/or reproducing apparatusshown in FIG. 5.

[0060]FIG. 7 illustrates an input/output example in a decoder applied toa reproducing system of the magnetic recording and/or reproducingapparatus shown in FIG. 5.

[0061]FIG. 8 is a block diagram for illustrating the structure of adecoder used in the reproducing system of the magnetic recording and/orreproducing apparatus shown in FIG. 5.

[0062]FIG. 9 is a block diagram for illustrating the structure of therecording and/or reproducing apparatus shown in FIG. 5.

[0063]FIG. 10 is a block diagram for illustrating the structure of achannel and a modulation turbo decoder provided in the reproducingsystem of the recording and/or reproducing apparatus shown in FIG. 5.

[0064]FIG. 11 illustrates the status transition diagram for generatingcodes satisfying the (d, k)=(0, 2) limitations.

[0065]FIG. 12 illustrates the trellis when status transition hasoccurred thrice in accordance with the status transition diagram shownin FIG. 11.

[0066]FIG. 13 illustrates the trellis constructed on branch selectionfrom the trellis shown in FIG. 12.

[0067]FIG. 14 is a block diagram showing the structure of an encoderused in a recording system of a magnetic recording and/or reproducingapparatus shown as a second embodiment of the present invention.

[0068]FIG. 15 is a block diagram for illustrating the structure of themagnetic recording and/or reproducing apparatus.

[0069]FIG. 16 is a block diagram for illustrating the structure of thechannel and a modulation turbo decoder provided in a reproducing systemof the magnetic recording and/or reproducing apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0070] Referring to the drawings, preferred embodiments of the presentinvention will be explained in detail.

[0071] The present embodiment is directed to a magnetic recording and/orreproducing apparatus made up of a recording system for recording dataon a recording medium of the magnetic recording system, such as a harddisc or a so-called DVCR (digital video cassette recorder), and areproducing system for reproducing data recorded on these recordingmediums.

[0072] This magnetic recording and/or reproducing apparatus includes, inits recording system, an interleaver downstream of a modulation encoder,adapted for modulating signals, and executes encoding by so-calledserial concatenated coding between a modulation encoder and a precoder,adapted for performing filtering on signals, in such a manner as tocompensate for channel characteristics. Moreover, the magnetic recordingand/or reproducing apparatus uses, on the reproducing side, a decoderfor the channel and a decoder for modulation decoding the modulationencoded signals, that is an SISO (soft input soft output) type decoder,fed with soft input data to output soft output data, and iterativelyexecutes decoding between these two decoders. This decoding is termedturbo decoding. That is, the magnetic recording and/or reproducingapparatus applies the encoding by the serial concatenated code and turbodecoding, known as the encoding method and decoding method giving theperformance close to the Shannon limit as set by what is called theShannon's theorem on the channel coding, to a recording and/orreproducing system performing data recording and/or reproduction for arecording medium.

[0073] First, the magnetic recording and/or reproducing apparatus as afirst embodiment is explained. Here, the interleaver, applied to therecording system of this magnetic recording and/or reproducingapparatus, is explained by referring to FIGS. 5 and 6.

[0074] An interleaver 10, shown in FIG. 5, interleaves data, encoded byblock modulation by a modulation encoder provided on a pre-stage of theinterleaver 10, on the modulation code block basis, that is on thesymbol basis, to re-array the bits making up the data. For example, ifthe interleaver 10 re-arrays respective bits of data modulation-encodedto generate 3 output bits for 2 input bits in accordance with aconversion table shown in the following Table 3, the interleaver 10re-arrays an input signal, fed in a unit of three bits, as a modulationencoder block unit, in a unit of three bits, as shown in FIG. 6, togenerate an output signal: TABLE 3 Example of Conversion Table inputbits output bits 00 011 01 101 10 111 11 110

[0075] More specifically, the interleaver 10 holds the interleavingposition information of data determined on the basis of generated randomnumbers in e.g., a ROM (read-only memory), and re-arrays the inputsignal on the modulation code block basis, based on the interleavingposition information. For example, the interleaver 10 holds theinterleaving position information of data making up an input signal, andre-arrays the bits on the modulation encoding block basis, in accordancewith the interleaving position information, at a timing of generation ofthe bit string made up of N bits, where N is an optional natural number,to output the re-arrayed bits as an output signal at a preset timing.

[0076] The decoder for modulation-decoding the modulation encodedsignals, as a SISO type decoder applied to the reproducing system of themagnetic recording and/or reproducing apparatus, is explained withreference to FIGS. 7 and 8. It should be noted that, although thedecoders 20, 30, shown in FIGS. 7 and 8, are shown as being the decodersfor modulation-decoding the modulation-encoded signals, the decoder forthe channel is to be realized in a similar manner.

[0077] A decoder 20, shown in FIG. 7, decodes data encoded by blockmodulation, with the code rate R=k/n, where k is the number of inputbits and n is the number of bits for modulation coding.

[0078] When fed with a reception signal R as the soft input, the decoder20 calculates the probability P (R_(i)=0|R) that the respective bits ofthis reception signal R are each “0” and the probability P (R_(i)=1|R)that the respective bits of this reception signal R are each “1”.Ultimately, the decoder 20 calculates a posterior probabilityinformation P (M_(i)=0|R) and P (M_(i)=1|R), as a soft decision valuefor a modulation code block M represented by M=(M₀, M₁, . . . ,M_(n-1)), and/or a posterior probability information P (C_(i)=0|R) and P(C_(i)=1|R), as a soft decision value for a modulation code input blockC represented by C=(C₀, C₁, . . . , C_(k-1)), to output theso-calculated information.

[0079] Instead of individually outputting the aforementioned posteriorprobability information, the decoder is also able to output thelogarithmic value of the ratio of the posterior probability information,that is log(P(M_(i)=1|R)/P(M_(i)=0|R)) orlog(P(C_(i)=1|R)/P(C_(i)=0|R)). These log values are routinely termedthe log likelihood ratio and here denote the likelihood of themodulating code block M and the modulating code input block C on theoccasion of inputting the reception signal R.

[0080] The decoder may also be fed with the priori probabilityinformation P (C_(i)=0) and P (C_(i)=1) for a modulation code inputblock C, instead of being fed with the aforementioned reception signalR.

[0081] Specifically, the decoder may, for example, be configured asshown in FIG. 8. In the following explanation, it is assumed that, forgenerating a three-bit output for a two-bit input, data to be decodedhas been encoded in accordance with the conversion table shown in Table3 given above.

[0082] The modulation decoder 30, shown in FIG. 8, includes sixlikelihood calculating circuits 31 ₁, 31 ₂, 31 ₃, 31 ₄, 31 ₅ and 31 ₆,as means for calculating the likelihood of each reception bit, fouradders 32 ₁, 32 ₂, 32 ₃ and 32 ₄ for summing the data, four log-sumcircuits 33 ₁, 33 ₂, 33 ₃ and 33 ₄ for performing the operations of log(e^(A)+e^(B)) on the two data A and B, four adders 34 ₁, 34 ₂, 34 ₃ and34 ₄ for summing two data, five comparators 35 ₁, 35 ₂, 36 ₁, 36 ₂ and36 ₃ for taking the ratio of the two data, coefficient calculatingcircuits 37 ₁, 37 ₂ and 37 ₃ for calculating coefficients for respectiveelements in the modulation encoding block M and three adders 38 ₁, 38 ₂and 38 ₃ for adding two data. It is noted that the number six of thelikelihood calculating circuits is derived from three bits multiplied by2 equals to six bits.

[0083] The likelihood calculating circuits 31 ₁, 31 ₂, 31 ₃, 31 ₄, 31 ₅and 31 ₆ are respectively fed with respective reception bits in areception signal D31 (R) to calculate the likelihood of the respectivereception bits.

[0084] That is, the likelihood calculating circuits 31 ₁ is fed with the0th bit of the three-bit reception signal D31 to calculate the logprobability value D32 ₁ (log P(R₀=0|R)) corresponding to the log valueof the probability that this bit is “0”. The likelihood calculatingcircuits 31 ₁ sends the generated log probability value D32 ₁ to theadder 32 ₁.

[0085] The likelihood calculating circuits 31 ₂ is fed with the 0th bitof the three-bit reception signal D31 to calculate the log probabilityvalue D32 ₂ (log P(R₀=1|R)) corresponding to the log value of theprobability that this bit is “1”. The likelihood calculating circuits 31₂ sends the generated log probability value D32 ₂ to the adders 32 ₂, 32₃ and 32 ₄ and to the comparator 36 ₁.

[0086] Then, the likelihood calculating circuits 31 ₃ is fed with thefirst bit of the three-bit reception signal D31 to calculate the logprobability value D32 ₃ (log P(R₁=0|R)) corresponding to the log valueof the probability that this bit is “0”. The likelihood calculatingcircuits 31 ₃ sends the generated log probability value D32 ₃ to theadder 32 ₂ and to the comparator 36 ₂.

[0087] The likelihood calculating circuits 31 ₄ is fed with the firstbit of the three-bit reception signal D31 to calculate the logprobability value D32 ₄ (log P(R₁=1|R)) corresponding to the log valueof the probability that this bit is “1”. The likelihood calculatingcircuits 31 ₄ sends the generated log probability value D32 ₄ to theadder 32 ₁, 32 ₃ and 32 ₄ and to the comparator 36 ₂.

[0088] Then, the likelihood calculating circuits 31 ₅ is fed with thesecond bit of the three-bit reception signal D31 to calculate the logprobability value D32 ₅ (log P(R₂=0|R)) corresponding to the log valueof the probability that this bit is “0”. The likelihood calculatingcircuits 31 ₅ sends the generated log probability value D32 ₅ to theadder 32 ₄ and to the comparator 36 ₃.

[0089] The likelihood calculating circuits 31 ₆ is fed with the secondbit of the three-bit reception signal D31 to calculate the logprobability value D32 ₆ (log P(R₂=1|R)) corresponding to the log valueof the probability that this bit is “1”. The likelihood calculatingcircuits 31 ₆ sends the generated log probability value D32 ₆ to theadders 32 ₁, 32 ₂ and 32 ₃ and to the comparator 36 ₃.

[0090] The adder D32 ₁ sums the log probability value D32 ₁, suppliedfrom the likelihood calculating circuits 31 ₁, the log probability valueD32 ₄, supplied from the likelihood calculating circuits 31 ₄ and thelog probability value D32 ₆, supplied from the likelihood calculatingcircuits 31 ₆, to generate the likelihood value D33 ₁. That is, thislikelihood value D33 ₁ is not other than the probability represented bylog P(R|M₀M₁M₂=011). The adder D32 ₁ sends the generated likelihoodvalue D33 ₁ to the log-sum circuits 33 ₁, 33 ₃.

[0091] The adder D32 ₂ sums the log probability value D32 ₂, suppliedfrom the likelihood calculating circuits 31 ₂, the log probability valueD32 ₃, supplied from the likelihood calculating circuits 31 ₃ and thelog probability value D32 ₆, supplied from the likelihood calculatingcircuits 31 ₆ to generate the likelihood value D33 ₂. That is, thislikelihood value D33 ₂ is not other than the probability represented bylog P(R|M₀M₁M₂=101). The adder D32 ₂ sends the generated likelihoodvalue D33 ₂ to the log-sum circuits 33 ₁, 33 ₄.

[0092] The adder D32 ₃ sums the log probability value D32 ₂, suppliedfrom the likelihood calculating circuits 31 ₂, the log probability valueD32 ₄, supplied from the likelihood calculating circuits 31 ₄, and thelog probability value D32 ₆, supplied from the likelihood calculatingcircuits 31 ₆, to generate the likelihood value D33 ₃. That is , thislikelihood value D33 ₃ is not other than the probability represented bylog P(R|M₀M₁M₂=111). The adder D32 ₃ sends the generated likelihoodvalue D33 ₃ to the log-sum circuits 33 ₂, 33 ₃.

[0093] The adder D32 ₄ sums the log probability value D32 ₂, suppliedfrom the likelihood calculating circuits 31 ₂, the log probability valueD32 ₄, supplied from the likelihood calculating circuits 31 ₄ and thelog probability value D32 ₅, supplied from the likelihood calculatingcircuits 31 ₅, to generate the likelihood value D33 ₄. That is, thislikelihood value D33 ₄ is not other than the probability represented bylog P(R|M₀M₁M₂=110). The adder D32 ₄ sends the generated likelihoodvalue D33 ₄ to the log-sum circuits 33 ₂, 33 ₄.

[0094] The log-sum circuit 33 ₁ performs an operation shown by theequation (4):

log(e ^(log P(R|M) ^(₀) ^(M) ^(₁) ^(M) ^(₂) ⁼⁰¹¹⁾ +e ^(log P(R|M) ^(₀)^(M) ^(₁) ^(M) ^(₂) ⁼¹⁰¹⁾)=log(P(R|M ₀ M ₁ M ₂=011)+P(R|M ₀ M ₁ M₂=101))  (4)

[0095] on the likelihood value D33 ₁ supplied from the adder 32 ₁ and onthe likelihood value D33 ₂ supplied from the adder 32 ₂ to generate alikelihood value D34 ₁. The log-sum circuit 33 ₁ sends the so-generatedlikelihood value D34 ₁ to the adder 34 ₁.

[0096] The log-sum circuit 33 ₂ performs an operation shown by theequation (5):

log(e ^(log P(R|M) ^(₀) ^(M) ^(₁) ^(M) ^(₂) ⁼¹¹¹⁾ +e ^(log P(R|M) ^(₀)^(M) ^(₁) ^(M) ^(₂) ⁼¹¹⁰⁾)=log(P(R|M ₀ M ₁ M ₂=111)+P(R|M ₀ M ₁ M₂=110))  (5)

[0097] on the likelihood value D33 ₃ supplied from the adder 32 ₃ and onthe likelihood value D33 ₄ supplied from the adder 32 ₄ to generate alikelihood value D34 ₂. The log-sum circuit 33 ₂ sends the so-generatedlikelihood value D34 ₂ to the adder 34 ₂.

[0098] The log-sum circuit 33 ₃ performs an operation shown by theequation (6):

log(e ^(log P(R|M) ^(₀) ^(M) ^(₁) ^(M) ^(₂) ⁼⁰¹¹⁾ +e ^(log P(R|M) ^(₀)^(M) ^(₁) ^(M) ^(₂) ⁼¹¹¹⁾)=log(P(R|M ₀ M ₁ M ₂=011)+P(R|M ₀ M ₁ M₂=111))  (6)

[0099] on the likelihood value D33 ₁ supplied from the adder 32 ₁ and onthe likelihood value D33 ₃ supplied from the adder 32 ₃ to generate alikelihood value D34 ₃. The log-sum circuit 33 ₃ sends the so-generatedlikelihood value D34 ₃ to the adder 34 ₃.

[0100] The log-sum circuit 33 ₄ performs an operation shown by theequation (7):

log(e ^(log P(R|M) ^(₀) ^(M) ^(₁) ^(M) ^(₂) ⁼¹⁰¹⁾ +e ^(log P(R|M) ^(₀)^(M) ^(₁) ^(M) ^(₂) ⁼¹¹⁰⁾)=log(P(R|M ₀ M ₁ M ₂=101)+P(R|M ₀ M ₁ M₂=110))  (7)

[0101] on the likelihood value D33 ₂ supplied from the adder 32 ₂ and onthe likelihood value D33 ₄ supplied from the adder 32 ₄ to generate alikelihood value D34 ₄. The log-sum circuit 33 ₄ sends the so-generatedlikelihood value D34 ₄ to the adder 34 ₄.

[0102] The adder 34 ₁ sums the likelihood value D34 ₁ supplied from thelog-sum circuit 33 ₁ and the log priori probability D35 ₁ (log P(C₀=0))for an input bit, fed from outside, to generate the log probabilityvalue D36 ₁. This log probability value D36 ₁ denotes the probabilityshown by the following equation (8):

log P(C ₀=0|R)=log {P(R|M ₀ M ₁ M ₂=011)+(R|M ₀ M ₁ M ₂=101)}+logP(C₀=0)  (8).

[0103] The adder 34 ₁ sends the generated log probability value D36 ₁ toa comparator 35 ₁.

[0104] The adder 34 ₂ sums the likelihood value D34 ₂ supplied from thelog-sum circuit 33 ₂ and the log priori probability D35 ₂ (log P(C₀=1))for an input bit, input from outside, to generate the log probabilityvalue D36 ₂. This log probability value D36 ₂ denotes the probabilityshown by the following equation (9):

log P(C ₀=1|R)=log {P(R|M ₀ M ₁ M ₂=111)+(R|M ₀ M ₁ M ₂=110)}+log P(C₀=1)  (9).

[0105] The adder 34 ₂ sends the generated log probability value D36 ₂ toa comparator 35 ₁.

[0106] The adder 34 ₃ sums the likelihood value D34 ₃ supplied from thelog-sum circuit 33 ₃ and the log priori probability D35 ₃ (log P(C₁=0))for an input bit, input from outside, to generate the log probabilityvalue D36 ₃. This log probability value D36 ₃ denotes the probabilityshown by the following equation (10):

log P(C ₁=0|R)=log {P(R|M ₀ M ₁ M ₂=011)+(R|M ₀ M ₁ M ₂=111)}+log P(C₁=0)  (10).

[0107] The adder 34 ₃ sends the generated log probability value D36 ₃ tothe comparator 35 ₂.

[0108] The adder 34 ₄ sums the likelihood value D34 ₄ supplied from thelog-sum circuit 33 ₄ and the log priori probability D35 ₄ (log P(C₁=1))for an input bit, input from outside, to generate the log probabilityvalue D36 ₄. This log probability value D36 ₄ denotes the probabilityshown by the following equation (11):

log P(C ₁=1|R)=log {P(R|M ₀ M ₁ M ₂=101)+(R|M ₀ M ₁ M ₂=110)}+log P(C₁=1)  (11).

[0109] The adder 34 ₄ sends the generated log probability value D36 ₄ toa comparator 35 ₂.

[0110] The comparator 35 ₁ takes the ratio of the log probability valueD36 ₁ supplied from the adder 34 ₁ and the log probability value D36 ₂supplied from the adder 34 ₂ to generate the decoded log posteriorprobability ratio D37 ₁ (log(P(C₀=1|R)/P(C₀=0|R))) which is output tooutside.

[0111] The comparator 35 ₂ takes the ratio of the log probability valueD36 ₃ supplied from the adder 34 ₃ and the log probability value D36 ₄supplied from the adder 34 ₄ to generate the decoded log posteriorprobability ratio D37 ₂ (log(P(C₁=1|R)/P(C₁=0|R))) which is output tooutside.

[0112] The comparator 36 ₁ takes the ratio of the log probability valueD32 ₁ supplied from the likelihood calculating circuit 31 ₁ and the logprobability value D32 ₂ supplied from the likelihood calculating circuit31 ₂ to generate the log posterior probability ratio D38 ₁(log(P(M₀=1|R)/P(M₀=0|R))) which is output to the adder 38 ₁.

[0113] The comparator 36 ₂ takes the ratio of the log probability valueD32 ₃ supplied from the likelihood calculating circuit 31 ₃ and the logprobability value D32 ₄ supplied from the likelihood calculating circuit31 ₄ to generate the log posterior probability ratio D38 ₂(log(P(M₁=1|R)/P(M₁=0|R))) which is output to the adder 38 ₂.

[0114] The comparator 36 ₃ takes the ratio of the log probability valueD32 ₅ supplied from the likelihood calculating circuit 31 ₅ and the logprobability value D32 ₆ supplied from the likelihood calculating circuit31 ₆ to generate the log posterior probability ratio D38 ₃(log(P(M₂=1|R)/P(M₂=0|R))) which is output to the adder 38 ₃.

[0115] The coefficient calculating circuit 37 ₁ calculates the M₀coefficient, represented by the following equation (12): $\begin{matrix}{\alpha = {{\log {{P\left( {C_{0} = 0} \right)} \cdot {P\left( {C_{1} = 1} \right)}}} + {{P\left( {C_{0} = 1} \right)} \cdot \quad {P\left( {C_{1} = 0} \right)}} + \frac{{P\left( {C_{0} = 1} \right)} \cdot {P\left( {C_{1} = 1} \right)}}{{P\left( {C_{0} = 0} \right)} \cdot {P\left( {C_{1} = 0} \right)}}}} & (12)\end{matrix}$

[0116] that is a coefficient α for the modulation code M₀ equivalent tothe 0th bit making up the three-bit reception signal D31, based on thelog priori probability D35 ₁, D35 ₂, D35 ₃ and D35 ₄ for the input bitsupplied from outside, to generate a M₀ coefficient signal D39 ₁. Thecoefficient calculating circuit 37 ₁ sends the generated M₀ coefficientD39 ₁ to the adder 38 ₁.

[0117] The coefficient calculating circuit 37 ₂ calculates the M₁coefficient, represented by the following equation (13): $\begin{matrix}{{\beta = {{\log {{P\left( {C_{0} = 0} \right)} \cdot {P\left( {C_{1} = 0} \right)}}} + {P\left( {C_{0} = 1} \right)}}}\quad {{P\left( {C_{1} = 0} \right)} + \frac{{P\left( {C_{0} = 1} \right)} \cdot {P\left( {C_{1} = 1} \right)}}{{P\left( {C_{0} = 1} \right)} \cdot {P\left( {C_{1} = 1} \right)}}}} & (13)\end{matrix}$

[0118] that is a coefficient β for the modulation code M₁ equivalent tothe first bit making up the three-bit reception signal D31, based on thelog priori probability D35 ₁, D35 ₂, D35 ₃ and D35 ₄ for the input bitsupplied from outside, to generate a M₁ coefficient signal D39 ₂. Thecoefficient calculating circuit 37 ₂ sends the generated M₁ coefficientD39 ₂ to the adder 38 ₂.

[0119] The coefficient calculating circuit 37 ₃ calculates the M₂coefficient, represented by the following equation (14): $\begin{matrix}{{\gamma = {{\log {{P\left( {C_{0} = 0} \right)} \cdot {P\left( {C_{1} = 0} \right)}}} + {P\left( {C_{0} = 0} \right)}}}\quad {{P\left( {C_{1} = 1} \right)} + \frac{{P\left( {C_{0} = 1} \right)} \cdot {P\left( {C_{1} = 0} \right)}}{{P\left( {C_{0} = 1} \right)} \cdot {P\left( {C_{1} = 1} \right)}}}} & (14)\end{matrix}$

[0120] that is a coefficient γ for the modulation code M₂ equivalent tothe second bit making up the three-bit reception signal D31, based onthe log priori probability D35 ₁, D35 ₂, D35 ₃ and D35 ₄ for the inputbit supplied from outside, to generate a M₂ coefficient signal D39 ₃.The coefficient calculating circuit 37 ₃ sends the generated M₂coefficient D39 ₃ to the adder 38 ₃.

[0121] The adder 38 ₁ sums the log posterior probability ratio D38 ₁,supplied from the comparator 36 ₁, to the M₁ coefficient signal D39 ₁supplied from the coefficient calculating circuit D37 ₁. The adder 38 ₁outputs the decoded channel log posterior probability ratio signal D40₁(log(P(M₀=1|R)/P(M₀=0|R))) to outside.

[0122] The adder 38 ₂ sums the log posterior probability ratio D38 ₂,supplied from the comparator 36 ₂, to the M₁ coefficient signal D39 ₂supplied from the coefficient calculating circuit D37 ₂. The adder 38 ₂outputs the decoded channel log posterior probability ratio signal D40₂(log(P(M₁=1|R)/P(M₁=0|R))) to outside.

[0123] The adder 38 ₃ sums the log posterior probability ratio D38 ₃,supplied from the comparator 36 ₃, to the M₂ coefficient signal D39 ₃supplied from the coefficient calculating circuit D37 ₃. The adder 38 ₃outputs the decoded channel log posterior probability ratio signal D40₃(log(P(M₂=1|R)/P(M₂=0|R))) to outside.

[0124] The decoder 30, having the components as described above, has thelikelihood calculating circuits 31 ₁, 31 ₂, 31 ₃, 31 ₄, 31 ₅ and 31 ₆for calculating the likelihood of respective reception bits in thereception signals D31 (R) taking analog values under the effect of thenoise generated in the course of transmission, as soft input, that isthe respective output codewords on the modulation coder side. By theselikelihood calculating circuits 31 ₁, 31 ₂, 31 ₃, 31 ₄, 31 ₅ and 31 ₆,the modulation decoder 30 finds the likelihood of the respectivecodewords and uses the likelihood values, thus found, to find theposterior probability information straightforwardly, as soft decisionvalues for the input and output bits on the modulation coder side.

[0125] Meanwhile, the decoder 30 is fed from outside with log prioriprobability D35 ₁, D35 ₂, D35 ₃, D35 ₄ If the probability of therespective bits making up the binary signal input to the modulationcoder, not shown, being “0”, is equivalent to the same probability being“1”, there is no necessity of inputting the log priori probability D35₁, D35 ₂, D35 ₃, D35 ₄, it being only necessary to handle as if thevalues of these log priori probability D35 ₁, D35 ₂, D35 ₃, D35 ₄ areall equal to zero.

[0126] Although the above explanation is based on the assumption thatthe modulation decoder 30 decodes data obtained on modulation-coding a2-bit input to a 3-bit output, the modulation decoder is not limited asto the number of bits of the input or the output and may be similarlyconfigured in keeping with the number of bits of the input or the outputused.

[0127] Referring to FIG. 9, the magnetic recording and/or reproducingapparatus, employing this interleaver and decoder, is hereinafterexplained.

[0128] A magnetic recording and/or reproducing apparatus 50, shown inFIG. 9, includes, as a recording system for recording data on arecording medium 70, an error correction coder 51 for error correctioncoding input data, a modulation coder 52 for modulation coding inputdata, an interleaver 53 for re-arraying the input data, a precoder 54for filtering the input data for compensating for channelcharacteristics, a write current driver 55 for converting respectivebits of the input data into write current values, and a write head 56for recording data on a recording medium 70.

[0129] The error correction coder 51, as error correction encodingmeans, applies error correction coding to the input data D51. The errorcorrection coder 51 sends the error correction encoded data D52,generated on error correction coding, to the downstream side modulationencoder 52.

[0130] The modulation encoder 52, as modulation encoding means, appliespredetermined modulation coding to the error correction encoded dataD52, supplied from the error correction coder 51, to generate modulationencoded data D53 as a string subjected to limitations. The modulationencoder 52 sends the so-generated modulation encoded data D53 to thedownstream side interleaver 53.

[0131] The interleaver 53, as (first) interleaving means, is constructedas the aforementioned interleaver 10, interleaving the modulationencoded data D53, encoded with block modulation by the modulationencoder 52, on the modulation encoding block basis, to re-array thesequence of bits making up the modulation encoded data D53. Theinterleaver 53 sends the generated interleaved data D54 to thedownstream side precoder 54.

[0132] The precoder 54 as preceding means filters the interleaved dataD54, supplied from the interleaver 53, in such a manner as to compensatefor channel characteristics from the data writing to the recordingmedium 70 to the outputting thereof in the equalizer 58 in thereproducing system, thereby generating a precode signal D55 as a binarysignal. For example, if the channel has 1-D characteristics the precoder54 performs filtering F represented by the following equation (15):

F=1/(1⊕D)  (15)

[0133] where ⊕ denotes exclusive-OR. The precoder 54 sends the generatedprecode signal D55 to the downstream side write current driver 55.

[0134] The write current driver 55 converts respective bits of theprecode signal D55, supplied from the precoder 54, into the writecurrent value I_(S), so that 0 and 1 will be converted to −I_(S) and+I_(S) (0→−I_(S), 1→+I_(S)), respectively, to generate a write currentsignal D56. The write current driver 55 sends the so-generated writecurrent signal D56 to the downstream side write head 56.

[0135] The write head 56 routes a write magnetic signal D57, conformingto the write current signal D56, supplied from the write current driver55, to the recording medium 70 to record data thereon.

[0136] When recording data on the recording medium 70, the recordingsystem in this magnetic recording and/or reproducing apparatus 50applies error correction coding to the input data D51, by the errorcorrection coder 51, to produce error correction coded data D52, whichthen is modulation-encoded in a predetermined fashion by the modulationcoder 52. The so-produced modulation encoded data D53 is interleaved bythe interleaver 53 on the modulation encoding block basis to produceprecode signal D55 by the precoder 54.

[0137] The recording system records the precode signal D55, generated bythe precoder 54, on the recording medium 70, through the write head 55and the write head 56.

[0138] The recording system in the magnetic recording and/or reproducingapparatus includes the interleaver 53 downstream of the modulationencoder 52, and executes serial concatenated coding between themodulation encoder 52 and the precoder 54 to realize high performanceencoding as encoding downstream of the error correction coding andencoding for the channel.

[0139] On the other hand, the magnetic recording and/or reproducingapparatus 50 includes, as a reproducing system for reproducing the datarecorded on the recording medium 70, a readout head 57 for reading outdata recorded on the recording medium 70, an equalizer 58 for equalizinginput data, a gain adjustment circuit 59 for adjusting the gain of theinput data, an analog/digital (A/D) converter 60 for converting analogdata into digital data, a timing reproducing circuit 61 for reproducingclocks, a gain adjustment control circuit 62 for controlling the gainadjustment circuit 59, a channel and modulation turbo decoder 63 forapplying turbo soft decoding to the input data, and an error correctingsoft decoder 64 for applying error correcting soft decoding to the inputdata.

[0140] The readout head 57 reads out a readout magnetization signal D58from the recording medium and generates a readout current signal D59corresponding to this readout magnetization signal D58. The readout head57 sends the generated readout current signal D59 to the downstream sideequalizer 58.

[0141] The equalizer 58 equalizes the readout current signal D59,supplied from the readout head 57, so that the channel response fromdata writing on the recording medium 70 in the recording system up tooutputting thereof in the equalizer 58 will be of pre-setcharacteristics, such as 1-D, to generate an equalized signal D60. Theequalizer 58 sends the generated equalized signal D60 to the downstreamside gain adjustment circuit 59.

[0142] The gain adjustment circuit 59 adjusts the gain of the equalizedsignal D60, supplied from the equalizer 58, based on the gain adjustmentcontrol signal D64 supplied from the gain adjustment control circuit 62,to generate a gain adjustment signal D61. The gain adjustment circuit 59sends the generated gain adjustment signal D61 to the downstream sideA/D converter 60.

[0143] The A/D converter 60 samples the gain adjustment signal D61,supplied from the gain adjustment circuit 59, based on the clock signalD63 supplied from the timing generating circuit 61, to digitize the gainadjustment signal D61 to generate a digital channel signal D62. The A/Dconverter 60 sends the so-generated digital channel signal D62 to thetiming generating circuit 61, gain adjustment control circuit 62 and tothe channel and modulation turbo decoder 63.

[0144] The timing generating circuit 61 regenerates clocks from thedigital channel signal D62, supplied from the A/D converter 60, togenerate clock signals D63. The timing generating circuit 61 routes thegenerated clock signals D63 to the A/D converter 60.

[0145] Based on the digital channel signal D62, supplied from the A/Dconverter 60, the gain adjustment control circuit 62 generates a gainadjustment control signal D64, which is a control signal used formaintaining the amplitude of the equalized signal D60 at an expectedvalue. The gain adjustment control circuit 62 sends the generated gainadjustment control signal D64 to the gain adjustment circuit 59.

[0146] The channel and modulation turbo decoder 63 concatenates SISOdecoders, constructed as the above-mentioned decoders 20, 30, to executeturbo decoding. The channel and modulation turbo decoder 63, explainedlater in detail, is fed with the digital channel signal D62, suppliedfrom the A/D converter 60, to perform turbo decoding, and routes aso-generated turbo decoded signal D65 to the post-stage error correctingsoft decoder 64.

[0147] The error correcting soft decoder 64, as error correction softdecoding means, applies the so-called BCJR (Bahl, Cocke, Jelinek andRahiv) algorithm or the SOVA (soft output viterbi algorithm) to theturbo decoded signal D65, supplied from the channel and modulation turbodecoder 63, to output the soft-decoded signal as soft or hard outputdata D66.

[0148] The channel and modulation turbo decoder 63 will be explained indetail by referring to FIG. 10.

[0149] Referring to FIG. 10, the channel and modulation turbo decoder 63includes a channel SISO decoder 81, as an SISO type decoder for decodingthe channel response from the pre-stage of the precoder 54 in therecording system up to the outputting stage of the equalizer 58 in thereproducing system, a deinterleaver 83 for restoring the sequence of theinput data to the original sequence, a modulation SISO decoder 84, as adecoder of the SISO type for modulation decoding the input data, adeinterleaver 86 for re-arraying the input data, a changeover switch 87for switching the data input as the priori probability information toinformation bits and two difference taking units 82, 85.

[0150] The channel SISO decoder 81, as channel decoding means, isconstructed as the aforementioned decoders 20, 30, and is an SISO typedecoder. The channel SISO decoder 81 is fed with the digital channelsignal D62, as a soft input supplied from the A/D converter 60, and withthe priori probability information D78, which is the priori probabilityinformation D76 for an information bit as a soft input supplied from theinterleaver 86, or the priori probability information D77 for aninformation bit which is of a value “0”, as selected by the changeoverswitch 87, and performs soft output decoding, based on the channelresponse R_(ch) from the pre-stage of the precoder 54 in the recordingsystem up to an output in the equalizer 58, represented by the followingequation (13):

R _(ch)=(1-D)/(1⊕D)  (16)

[0151] where ⊕ denotes exclusive OR, in accordance with theaforementioned BCJR algorithm or SOVA. If the interleaved data D54 priorto the precoding by the precoder 54 is represented as C(t), with 0≦t≦N,the channel SISO decoder 81 computes the log posterior probability ratiolog (P(C(t)=1)/P(C(t)=0)), as the posterior probability information forC(t), to route this log posterior probability ratio as the channeldecoded signal D71 to the downstream side difference taking unit 82.

[0152] The channel SISO decoder 81 is not limited to the aforementioneddecoders 20, 30, it being only sufficient if the channel SISO decoder 81is constructed as an SISO decoder. For example, it is sufficient if thechannel SISO decoder 81 performs soft output decoding, in accordancewith the aforementioned BCJR algorithm or SOVA, based on the trelliscorresponding to the channel response.

[0153] The difference taking unit 82 takes the difference between thechannel decoded signal D71, as a soft input, supplied from the channelSISO decoder 81, and the priori probability information D76, as a softinput, supplied from the interleaver 86, to output data represented byths difference value as a soft output to the post-stage deinterleaver83, as the channel extrinsic information signals D72 as the extrinsicinformation to an information bit as found by the code constraintcondition. Meanwhile, this channel extrinsic information signals D72corresponds to the interleaved data D54 as interleaved by theinterleaver 53 of the recording system.

[0154] The deinterleaver 83, as deinterleaving means, deinterleaves thechannel extrinsic information signals D72, as a soft input, suppliedfrom the difference taking unit 82, in order to restore the bit sequenceof the interleaved data D54 from the interleaver 53 of the recordingsystem to the bit sequence of the original modulation encoded data D53.The deinterleaver 83 sends the deinterleaved data to the modulation SISOdecoder 84 and to the difference taking unit 85 as the deinterleavedsignal D73 which is the priori probability information to the code bitin the modulation SISO decoder 84.

[0155] The modulation SISO decoder 84 as modulation decoding means isconstructed as the aforementioned decoders 20, 30 and is an SISOdecoder. It is assumed that the modulation encoding is applied by themodulation coder 52 of the recording system with the code rate R=K/N,with the modulation encoded data D53 following modulation encoding bythe modulation coder 52 being M(t) (0≦t<N) and with the error correctioncoded data D52 prior to modulation encoding by the modulation coder 52being E(t) (0≦t<K). The modulation SISO decoder 84, fed as an input withthe deinterleaved signal D73 from the deinterleaver 83, calculates thelog posterior probability ratio log (P(M(t)=1)/P(M(t)=0)), as theposterior probability information for M(t), with the deinterleavedsignal D73 as an input from the channel, and sends the log posteriorprobability ratio as the modulation channel decoded signal D74 to thedifference taking unit 85. The modulation SISO decoder 84 alsocalculates the log posterior probability ratio log(P(E(t)=1)/P(E(t)=0)), as the posterior probability information forE(t), to route the log posterior probability ratio as the turbo decodedsignal D65 to the error correcting soft decoder 64.

[0156] The difference taking unit 85 finds a difference value betweenthe modulation channel decoded signal D74, as a soft input, suppliedfrom the modulation SISO decoder 84, and the deinterleaved signal D73 asa soft input from the deinterleaver 83, and outputs data given as thisdifference value to the post-stage interleaver 86 as a soft output asthe modulated extrinsic information signals D75 as the extrinsicinformation to the code bit as found by the constraint condition.

[0157] The interleaver 86, as the second interleaving means, interleavesthe modulated extrinsic information signals D75, as a soft input fedfrom the difference taking unit 85, based on the same interleavingposition information as that of the interleaver 53 of the recordingsystem. The interleaver 86 sends the interleaved data to the channelSISO decoder 81 and to the difference taking unit 82 as being the prioriprobability information signal D76 for the information bit in thechannel SISO decoder 81.

[0158] In the initial stage of the decoding, the changeover switch 87 isset to the fixed terminal a supplying a value 0 corresponding to thepriori probability information signal D77 to select the prioriprobability information signal D77 as being the priori probabilityinformation signal D78 for an information bit in the channel SISOdecoder 81. The changeover switch 87 then is set to a fixed terminal bsupplying the priori probability information signal D76 supplied fromthe interleaver 86 to select the priori probability information signalD76 as being the priori probability information signal D78.

[0159] The channel and modulation turbo decoder 63, is provided with themodulation SISO decoder 84 and the channel SISO decoder 81, ascounterparts to the modulation coder 52 and the precoder 54 of therecording system, respectively, as described above, to decompose thecode of high decoding complexity into elements with lower decodingcomplexity, such as to sequentially improve characteristics by theinteraction between the channel SISO decoder 81 and the modulation SISOdecoder 84. If fed with the digital channel signal D62, as a soft input,from the A/D converter 60, the channel and modulation turbo decoder 63iterates the decoding operations from the channel SISO decoder 81 to themodulation SISO decoder 84 a pre-set number of times, such as several totens of times, to route the soft-output log posterior probability ratio,obtained on decoding a pre-set number of times, as the turbo decodedsignal D65 to the post-stage error correcting soft decoder 64.

[0160] In reproducing data recorded on the recording medium 70, thereproducing system of the magnetic recording and/or reproducingapparatus 50 turbo-decodes the soft-input digital channel signal D62,generated through the readout head 57, equalizer 58, gain adjustmentcircuit 59 and the A/D converter 60, by the channel and modulation turbodecoder 63, to generate the turbo decoded signal D65 corresponding tothe error correction coded data D52 input to the modulation coder 52 inthe recording system.

[0161] This reproducing system soft-decodes the turbo decoded signalD65, generated by the channel and modulation turbo decoder 63, for errorcorrection codes, by the error correcting soft decoder 64, to outputdata as resulting soft output directly to outside as output data D66, orbinary-codes the soft-output data to generate hard-output data D66,which is issued to outside.

[0162] The reproducing system of the magnetic recording and/orreproducing apparatus 50 is provided in this manner with the channel andmodulation turbo decoder 63 and performs turbo decoding between themodulation SISO decoder 84 and the channel SISO decoder 81 correspondingto the modulation coder 52 and the precoder 54 of the recording systemto realize decoding in meeting with the channel response and themodulation encoding.

[0163] In the above-described magnetic recording and/or reproducingapparatus 50, in which the interleaver 53 is provided in the recordingsystem on the post-stage of the modulation coder 52 to execute encodingby serial concatenated code between the modulation coder 52 and theprecoder 54, while it is provided on the reproducing system with thechannel and modulation turbo decoder 63 to effect turbo decoding torealize high performance coding. In addition, turbo decoding with highefficiency can be realized by exploiting soft information for the entiredecoding processing for the code, thus eliminating the necessity ofdiminishing the information. The result is the appreciably lowereddecoding error rate.

[0164] The second embodiment of the magnetic recording and/orreproducing apparatus is now explained. The magnetic recording and/orreproducing apparatus executes encoding as correlation is afforded tofore and aft side data instead of coding/decoding on the block basis. Inaddition, the magnetic recording and/or reproducing apparatus performstrellis decoding conforming to the constraint condition.

[0165] An interleaver used for the recording system of the magneticrecording and/or reproducing apparatus is first explained.

[0166] An interleaver applied to the recording system, such a one may beused which is configured similarly to the interleaver 10 shown in FIG. 5and in which data is interleaved based on the modulation encoding blockof the trellis to re-array the data bit sequence. It is assumed herethat the bit sequence of the data from the modulation encoding ofgenerating three output bits for two input bits in accordance with theconversion table shown in Table 3 by an interleaver. If the constraintcondition to be met by the modulation encoded data is (d, k)=(0, 2)limitation, the interleaver generates a sequence meeting the (d, k)=(0,4) limitation.

[0167] The interleaver is not limited to one interleaving the data basedon the modulation encoding block of the trellis, such that any suitableinterleaver interleaving the data such as to meet the pre-set constraintcondition following interleaving may be used.

[0168] Referring to FIGS. 11 to 14, the encoder used in the recordingsystem and the SISO decoder used for the reproducing system of themagnetic recording and/or reproducing apparatus is explained. It isnoted that, although the coder and the decoder, used for modulationencoding and modulation decoding, respectively, are shown here, thecoder and the decoder for the channel are configured in a similarfashion.

[0169] The magnetic recording and/or reproducing apparatus performsmodulation encoding and modulation decoding, based on a common trellis.Although the trellis structure is changed depending on limitationsimposed on the modulation code, the modulation encoding and modulationdecoding, satisfying the (d, k)=(0, 2) limitations, with the code rateR=2/3, is here explained.

[0170]FIG. 11 shows a diagram showing the status transition forgenerating satisfying the (d, k)=(0, 2) limitations. In FIG. 11, labelsaffixed between the respective states indicate bits output in case ofstatus transition. For example, if the status transition that hasoccurred is “S0→S1→S2”, an output bit string is “00”. The bit stringoutput in case status transition has occurred in accordance with theaforementioned status transition diagram necessarily satisfies the (d,k)=(0, 2) limitations.

[0171] Assume that the modulation encoding of outputting a 3 bitmodulated code for a 2-bit input, with the code rate R=2/3. Forgenerating the modulation code satisfying the (d, k)=(0, 2) limitations,it is apparently sufficient if status transition occurs thrice inaccordance with the status transition diagram shown in FIG. 11, with theresulting output being a modulated code.

[0172] The trellis when the status transition has occurred thrice inaccordance with the status transition diagram shown in FIG. 11, that is,a diagram obtained on developing the status transition diagram along thetime axis direction, is as shown in FIG. 12. For example, in the trellisshown in FIG. 12, a branch lying at an uppermost position indicates thatthere is one path starting at the status S2 and again getting to thestatus S2 after three status transitions, with a corresponding outputbeing “100”.

[0173] In case of modulation encoding of outputting 3-bit modulated codefor a 2-bit input, 2²=4 branches are selected from each state, thesebranches being then allocated to 2-bit inputs of “00, 01, 10, 11” toform a trellis in which an input is associated with an output. FIG. 13shows a trellis formed on branch selection as described above. In FIG.13, each label affixed between different states indicate aninput/output. For example, in the trellis shown in FIG. 13, a branchS0→S2 indicates that, if “11” is input for the state S0, statustransition occurs to the status S2, as “100” is output.

[0174] The encoder, applied to the magnetic recording and/or reproducingapparatus, shown as the second embodiment, repeats the status transitionfor encoding, in accordance with the trellis formed by theabove-described sequence of operations, to generate a modulated codestring having correlation between input data. The encoder may beprovided with components shown for example in FIG. 14.

[0175] The encoder 90, shown in FIG. 14, includes a state register 91for holding the state of the encoder 90, a next-state calculatingcircuit 92, for calculating the next transition state, and an outputsignal calculating circuit 93 for calculating an output signal D94.

[0176] The state register 91 is a 2-bit register holding 2 bitsspecifying the state of the current encoder 90. The state register 91sends a status signal D92, specifying the 2 bits indicating the currentstate, to the next-state calculating circuit 92 and to the output signalcalculating circuit 93, as the state register 91 holds 2 bits indicatingthe next state corresponding to the next state signal D93 supplied fromthe next-state calculating circuit 92.

[0177] When fed with the input signal D91 and with the status signalD92, supplied from the state register 91, the next-state calculatingcircuit 92 calculates the next state in accordance with the followinginput/output correlating table 4: TABLE 4 Typical Input/OutputCorrelating Table status signals input signals next-state signals 0 00 00 01 1 0 10 1 0 11 2 1 00 1 1 01 0 1 10 0 1 11 2 2 00 2 2 01 0 2 10 0 211 1 3 00 0 3 01 0 3 10 0 3 11 0

[0178] The next-state calculating circuit 92 sends the next state signalD93 to the state register 91.

[0179] If fed with the input signal D91 and with the status signal D92,supplied from the state register 91, the output signal calculatingcircuit 93 calculates an output signal D94, in accordance with thefollowing input/output correlating table 5: TABLE 5 Typical Input/OutputCorrelating Table status signals input signals output signals 0 00 111 001 110 0 10 010 0 11 100 1 00 110 1 01 011 1 10 111 1 11 100 2 00 100 201 101 2 10 111 2 11 110 3 00 111 3 01 111 3 10 111 3 11 111

[0180] Meanwhile, this output signal D94 satisfies the (d, k)=(0, 2)limitations.

[0181] When fed with the input signal D91, the encoder 90 calculates thenext state, using this input signal D91 and the status signal D92, bythe next-state calculating circuit 92, for storage sequentially in thestate register 91. The encoder 90 calculates an output signal D94, bythe output signal calculating circuit 93, using the input signal D91 andthe status signal D92, by the output signal calculating circuit 93, tooutput the so-calculated output signal D94.

[0182] Since there lacks the status S3 in the encoder 90, if transitionto the status S3 occurs before the resetting of the encoder 90, anoutput signal “111” is instantly output as an output signal D94, basedon the Table 5, to realize the function of resetting to the state S0.

[0183] A decoder for modulation decoding the signal, encoded by theabove-described encoder, applies the decoding, which is based on theBCJR or SOVA algorithm, in accordance with the trellis previouslyexplained with reference to FIG. 13. With this decoder, the magneticrecording and/or reproducing apparatus is able to perform trellisdecoding exploiting the signal correlation in the modulation encoder.

[0184] In particular, if, in performing trellis decoding in the magneticrecording and/or reproducing apparatus, SISO decoding of the BCJR orSOVA algorithm is used in the decoder, the soft information can beoutput to the error correction decoding circuit provided downstream ofthe modulation decoder, thereby improving the decoding error rate.

[0185] The magnetic recording and/or reproducing apparatus, employingthis type of the encoder and the decoder, is hereinafter explained withreference to FIG. 15.

[0186] The magnetic recording and/or reproducing apparatus 100, shown inFIG. 15, includes, as a recording system for recording data on arecording medium 70, an error correction encoder 101 for errorcorrection encoding input data, a modulation encoder 101, a modulationencoder 102 for modulation encoding input data, an interleaver 103 forre-arraying the input data in its sequence, a precoder 104 for filteringinput data for compensating its channel characteristics, a write currentdriver 105 for converting respective bits of the input data into writecurrent values, and a write head 106 for recording data on the recordingmedium 70.

[0187] Similarly to the error correction coder 51 in the magneticrecording and/or reproducing apparatus 50, the error correction encoder101, as error correcting encoding means, error correction encodes theinput data D101. The error correction encoder 101 sends the errorcorrection encoded data D102 to the downstream side modulation encoder102.

[0188] The modulation encoder 102, as modulation encoding means, isconfigured as the aforementioned modulation encoder 90. Specifically, itis a modulation encoder for repeating status transitions in accordancewith the trellis, by way of encoding, for generating a modulated codestring exhibiting correlation between input data. The modulation encoder102 applies pre-set trellis modulation coding to the error correctioncoded data D102, supplied from the error correction encoder 101, togenerate modulated encoded data D103 as a string subjected tolimitation. The modulation encoder 102 sends the generated modulationencoded data D103 to the downstream side interleaver 103.

[0189] The interleaver 103, as (first) interleaving means, interleavesthe modulated encoded data D103 in terms of the trellis modulationencoding block as a unit, to re-array the sequence of bits making up themodulated encoded data D103. The interleaver 103 sends the generatedinterleaved data D104 to the downstream side precoder 104.

[0190] Similarly to the precoder 54 of the aforementioned magneticrecording and/or reproducing apparatus 50, the precoder 104 filters theinterleaved data D104, supplied from the interleaver 103, in such amanner as to compensate for channel characteristics from the datawriting to the recording medium 70 to the output in the equalizer 108 inthe reproducing system, thereby generating a precode signal D105 as abinary signal. The precoder 104 sends the so-generated precede signalD105 to the downstream side write current driver 105.

[0191] Similarly to the write current driver 55 in the aforementionedmagnetic recording and/or reproducing apparatus 50, the write currentdriver 105 converts respective bits of the precode signal D104, suppliedfrom the precoder 103, into the write current value I_(S), to generate awrite current signal D106. The write current driver 105 sends thegenerated write current signal D106 to a downstream side write head 106.

[0192] Similarly to the write head 56 in the aforementioned magneticrecording and/or reproducing apparatus 50, the write head 106 applies amagnetic write signal D107, corresponding to the write current signalD106 supplied from the write current driver 105, to the recording medium70, to record data thereon.

[0193] In recording data on the recording medium 70, the recordingsystem in the magnetic recording and/or reproducing apparatus 100 errorcorrection encodes the input data D101 by the error correction encoder101. The recording system then applies pre-set trellis modulationencoding to error correction encoded data D102 by the modulation encoder102 and interleaves the modulated encoded data D103 by the interleaver103 based on the pre-set trellis modulation encoding block to generate aprecede signal D105 by the precoder 104.

[0194] The recording system records the precode signal D105, generatedby the precoder 104, on the recording medium 70, by the write currentdriver 105 and the write head 106.

[0195] The recording system of the magnetic recording and/or reproducingapparatus 100, thus having the interleaver 103 downstream of themodulation encoder 102, effects encoding by serial concatenated codingbetween the modulation encoder 102 and the precoder 104 to realize highperformance coding as modulation encoding and channel coding downstreamof the error correction coding.

[0196] As the reproducing system for reproducing data recorded on therecording medium 70, the magnetic recording and/or reproducing apparatus100 includes a readout head 107 for reading out data recorded on therecording medium 70, an equalizer 108 for equalizing input data, a gainadjustment circuit 109 for adjusting the gain of the input data, an A/Dcircuit 110 for converting analog data to digital data, a timing circuit111 for reproducing clocks, a gain adjustment control circuit 112 forcontrolling the gain adjustment circuit 109, a modulation turbo decoder113 for turbo-decoding the input data and an error correction softdecoder 104 for error correction soft decoding the input data.

[0197] Similarly to the readout head 57 of the magnetic recording and/orreproducing apparatus 50, a readout head 107 reads out the readoutmagnetization signal D108 from the recording medium 70 to generate areadout current signal D109 conforming to the readout magnetizationsignal D108. The readout head 107 sends the so-generated current signalD109 to the downstream side equalizer 108.

[0198] Similarly to the equalizer 58 of the magnetic recording and/orreproducing apparatus 50, the equalizer 108 equalizes the readoutcurrent signal D109, supplied from the readout head 107, so that thechannel response from the data writing on the recording medium 70 in therecording system up to the outputting at the equalizer 108 will be ofpre-set characteristics, to generate an equalized signal D110. Theequalizer 108 routes the generated equalized signal D110 to thedownstream side gain adjustment circuit 109.

[0199] Similarly to the gain adjustment circuit 59 Of the magneticrecording and/or reproducing apparatus 50, the gain adjustment circuit109 adjusts the gain of the equalized signal D110 supplied from theequalizer 108, based on a gain adjustment control signal D114, suppliedfrom the gain adjustment control circuit 112, to generate a gainadjustment signal D111. The gain adjustment circuit 109 routes thegenerated gain adjustment signal D111 to the downstream side A/Dconverter 110.

[0200] Similarly to the A/D converter 60 of the magnetic recordingand/or reproducing apparatus 50, the A/D converter 110 samples anddigitizes the gain adjustment signal D111, supplied from the gainadjustment circuit 109, based on the clock signal D113, supplied fromthe timing regenerating circuit 111, to generate a digital channelsignal D112. The A/D converter 110 sends the generated digital channelsignal D112 to the timing regenerating circuit 111, gain adjustmentcontrol circuit 112 and to the channel and modulation turbo decoder 113.

[0201] Similarly to the timing generating circuit 61 of the magneticrecording and/or reproducing apparatus 50, the timing regeneratingcircuit 111 regenerates clocks from the digital channel signal D112supplied from the A/ID converter 110 to generate clock signals D113. Thetiming regenerating circuit 111 sends the generated clock signals D113to the A/D converter 110.

[0202] Similarly to the gain adjustment control circuit 62 of themagnetic recording and/or reproducing apparatus 50, the gain adjustmentcontrol circuit 112 generates, based on the digital channel signal D112,supplied from the A/D converter 110, a gain adjustment control signalD114, which is a control signal used for maintaining the amplitude ofthe equalized signal D110 at an expected value. The gain adjustmentcontrol circuit 112 sends the generated gain adjustment control signalD114 to the gain adjustment circuit 109.

[0203] Similarly to the channel and modulation turbo decoder 63 of themagnetic recording and/or reproducing apparatus 50, the channel andmodulation turbo decoder 113, is comprised of concatenated SISO decodersto effect turbo decoding. The channel and modulation turbo decoder 113turbo-decodes the input digital channel signal D112 from the A/Dconverter 110 to route the generated turbo decoded signal D115 to thedownstream side error correction decoder 114.

[0204] Similarly to the error correction soft decoder 54 of the magneticrecording and/or reproducing apparatus 50, the error correction softdecoder 114, as error correcting soft decoding means, soft-decoded theturbo decoded signal D115 supplied from the modulation SISO decoder 113for errors based on the BCJR algorithm or SOVA to output soft or hardoutput data D116 to outside.

[0205] Referring to FIG. 16, the channel and modulation turbo decoder113 is explained in detail.

[0206] In this figure, the channel and modulation turbo decoder 113includes a channel SISO decoder 121, as an SISO decoder for decoding thechannel response from the pre-stage of the precoder 104 in the recordingsystem to the outputting in the equalizer 108, a deinterleaver 123 forrestoring the sequence of the input data, an SISO decoder 124, as a SISOdecoder for modulation decoding the input data, an interleaver 126 forre-arraying the sequence of the input data, a changeover switch 127 forchanging over input data input as the priori probability information forinformation bits and two difference taking units 122, 125.

[0207] The channel SISO decoder 121, as channel decoding means, is fedwith the digital channel signal D112, as a soft input supplied from theA/D converter 110, and with priori probability information D128, asselected by the changeover switch 127 from the priori probabilityinformation D126 for information bits supplied as soft input from theA/D converter 110 and the priori probability information D127 forinformation bits having a value of “0”, to effect soft output decoding,based on the BCJR algorithm or SOVA, in accordance with the trellis forthe channel response from the parentage of the precoder 104 in therecording system to an output in the equalizer 108 in the reproducingsystem. If the interleaved data D104 prior to precoding by the precoder104 is expressed as C(t) (0≦t≦N), the channel SISO decoder 121calculates the log posterior probability ratio log(P(C(t)=1)/P(C(t)=0)), as the posterior probability information for thisC(t), to send this log posterior probability ratio as the channeldecoded signal D121 to the downstream side difference taking unit 122.

[0208] The difference taking unit 122 finds a difference between thechannel decoded signal D121, as soft input, supplied from the channelSISO decoder 121, and the priori probability information D126, as softinput, supplied from the interleaver 126, to output data correspondingto this difference value as soft output to the downstream sidedeinterleaver 123 as the channel extrinsic information signals D122 foran information bit as found by the code constraint condition. Meanwhile,the channel extrinsic information signals D122 corresponds to theinterleaved data D104 obtained on interleaving by the interleaver 103 inthe recording system.

[0209] The deinterleaver 123, as deinterleaving means, deinterleaves thebit sequence of the interleaved data D104 from the interleaver 103 ofthe recording system to the channel extrinsic information signals D122supplied from the difference taking unit 122 in order to restore the bitsequence to that of the original modulated encoded data D103. Thedeinterleaver 123 sends the deinterleaved data to the modulation SISOdecoder 124 and to the difference taking unit 122 as the deinterleavedsignal D123 which is the priori probability information for the codebits in the modulation SISO decoder 124.

[0210] The modulation SISO decoder 124, as modulation decoding means,decodes signals encoded by the modulation encoder 102 in the recordingsystem, and is an SISO type modulation decoder. The modulation encodeddata D103, obtained on modulation encoding by the modulation encoder 102with a code rate R=K/N, is specified as M(t) (0≦t<N) and the errorcorrection encoded data D102 prior to modulation encoding by themodulation encoder 102 is specified as E(t) (0≦t<K). The modulation SISOdecoder 124 is fed with the deinterleaved signal D123, supplied as softinput from the deinterleaver 123, and calculates the log posteriorprobability ratio log (P(M(t)=1)/P(M(t)=0)), as posterior probabilityinformation for M(t), using the trellis corresponding to the constraintcondition, to send the so-calculated log posterior probability ratio asthe modulation channel decoded signal D124 to the difference taking unit125. The modulation SISO decoder 124 also calculates the log posteriorprobability ratio log (P(E(t)=1)/P(E(t)=0)), as posterior probabilityinformation for E(t), to send the so-calculated log posteriorprobability ratio as the turbo decoded signal D115 to the errorcorrection soft decoder 114.

[0211] The difference taking unit 125 finds a difference between themodulation channel decoded signal D124, supplied as soft input from themodulation SISO decoder 124, and the deinterleaved signal D123, suppliedas soft input from the deinterleaver 123, to output the data as thedifference value as soft output to the downstream side interleaver 126as the modulated extrinsic information signals D125, which is theextrinsic information for a code bit as found by the code constraintcondition.

[0212] The interleaver 126, as second interleaving means, interleavesthe modulated extrinsic information signals D125, supplied from thedifference taking unit 125, based on the same interleaving positioninformation as that of the interleaver 103 of the recording system. Theinterleaver 126 sends the interleaved data to the channel SISO decoder121 and to the difference taking unit 122 as being the prioriprobability information signal D126 for the information bit in thechannel SISO decoder 121.

[0213] In the initial stage of the decoding, the changeover switch 127is set to the fixed terminal c supplying a value 0 corresponding to thepriori probability information signal D127 to select the prioriprobability information signal D127 as being the priori probabilityinformation signal D128 for an information bit in the channel SISOdecoder 121. The changeover switch 127 then is set to a fixed terminal dsupplying the priori probability information signal D126 supplied fromthe interleaver 126 to select the priori probability information signalD126 as being the priori probability information signal D128.

[0214] Similarly to the channel and modulation turbo decoder 63 in thepreviously described magnetic recording and/or reproducing apparatus,the channel and modulation turbo decoder 113, is provided with themodulation SISO decoder 124 and the channel SISO decoder 121, ascounterparts to the modulation coder 102 and the precoder 104 of therecording system, respectively, as described above, to decompose thecode of high decoding complexity into elements with lower decodingcomplexity, such as to sequentially improve characteristics by theinteraction between the channel SISO decoder 121 and the modulation SISOdecoder 124. If fed with the digital channel signal D112, as a softinput, from the A/D converter 110, the channel and modulation turbodecoder 113 iterates the decoding operations from the channel SISOdecoder 121 to the modulation SISO decoder 124 a pre-set number oftimes, such as several to tens of times, to route the soft-output logposterior probability ratio, obtained on decoding a pre-set number oftimes, as the turbo decoded signal D115 to the post-stage errorcorrecting soft decoder 64.

[0215] In reproducing data recorded on the recording medium 70, thereproducing system of the magnetic recording and/or reproducingapparatus 50 turbo-decodes the soft-input digital channel signal D112,generated through the readout head 107, equalizer 108, gain adjustmentcircuit 109 and the A/D converter 110, by the channel and modulationturbo decoder 113, to generate the turbo decoded signal D115corresponding to the error correction coded data D102 input to themodulation coder 102 in the recording system.

[0216] This reproducing system soft-decodes error correction codes ofthe turbo decoded signal D115, generated by the channel and modulationturbo decoder 113, by the error correcting soft decoder 114, to outputdata as resulting soft output directly to outside as output data D116,or binary-codes the soft-output data to generate hard-output data D116which is issued to outside.

[0217] The reproducing system of the magnetic recording and/orreproducing apparatus 100 is provided in this manner with the channeland modulation turbo decoder 113 and performs turbo decoding between themodulation SISO decoder 124 and the channel SISO decoder 121corresponding to the modulation coder 102 and the precoder 104 of therecording system to realize decoding in meeting with the channelresponse and the modulation encoding.

[0218] The magnetic recording and/or reproducing apparatus 100 includes,in its recording system, the interleaver 103 downstream oft themodulation encoder 102, to effect encoding by serial concatenated codebetween the modulation encoder 102 and the precoder 104, whileincluding, on its reproducing side, the channel and modulation turbodecoder 113 to effect turbo decoding to realize high performance codingas well as highly efficient turbo decoding exploiting the softinformation for the entire decoding processing for the code. Since thereis no necessity of diminishing the information, the decoding error ratecan be lowered significantly. Moreover, the magnetic recording and/orreproducing apparatus 100 effects coding in the recording system, ascorrelation is afforded to the fore and aft side data. In addition,trellis decoding can be performed on the reproducing side in meetingwith the constraint condition, thus further lowering the decoding errorrate.

[0219] The above-described magnetic recording and/or reproducingapparatus 50, 100 are able to perform efficient turbo decoding byexploiting the soft information, thereby lowering the decoding errorrate. In particular, with the magnetic recording and/or reproducingapparatus 100, encoding can be made as correlation is afforded to thefore and aft side data, without doing block-based encoding or decoding,while trellis decoding can be made in meeting with the constraintconditions, thus further lowering the decoding error rate. That is, themagnetic recording and/or reproducing apparatus 50, 100 is able torealize high precision decoding, thus assuring high operationalreliability fort the user.

[0220] The present invention is not limited to the above-describedembodiment. For example, the present invention may be applied to arecording medium 70 other than the recording medium of the magneticrecording system, that is to a recording medium by the optical recordingsystem, such as a so-called CD (Compact Disc) or to the DVD (DigitalVersatile Disc) or to a recording medium of the photomagnetic recordingsystem, such as a so-called magneto-optical disc (MO) disc.

[0221] In the above-described embodiment, it is assumed that themagnetic recording and/or reproducing apparatus 100 performs trellismodulation encoding on the encoder side and trellis modulation decodingon the decoder side. However, the present invention is applicable tosuch a case wherein the trellis modulation decoding is performed on thedecoder side to output a soft decision value even in case the trellismodulation encoding is not performed on the encoding side, as when blockmodulation is effected on the encoder side.

[0222] Moreover, in the above-described embodiment, it is assumed thatthe magnetic recording and/or reproducing apparatus 50 or 100 is aunitary apparatus provided with the recording and reproducing systems.Alternatively, a unitary recording apparatus may be configured as arecording system for recording data on a recording medium, while aunitary reproducing apparatus may also be configured as a reproducingsystem for reproducing the data recorded on the recording apparatus.

[0223] In the foregoing, the present invention has been disclosed onlyby way of illustration and should not be interpreted in a limitingfashion. The scope of the present invention is to be interpreted inlight of the description of the following claims.

What is claimed is:
 1. A data recording apparatus for recording data ona recording medium, comprising: modulation encoding means for applyingpredetermined modulation encoding to input data; and interleaving meansfor interleaving data supplied from said modulation encoding means forre-arraying the data sequence.
 2. The data recording apparatus accordingto claim 1 further comprising: precoding means for filtering datasupplied from said interleaving means to compensate for channelcharacteristics.
 3. The data recording apparatus according to claim 1further comprising: error correction coding means for applying errorcorrection coding to the input data; said modulation encoding meansmodulation encoding the data supplied from said error correction codingmeans.
 4. The data recording apparatus according to claim 1 wherein saidmodulation encoding means encodes input data in accordance with aconstraint condition.
 5. The data recording apparatus according to claim4 wherein said interleaving means interleaves data encoded by saidmodulation encoding means so that said constraint condition issatisfied.
 6. The data recording apparatus according to claim 4 whereinsaid modulation encoding means encodes the input data by blockmodulation.
 7. The data recording apparatus according to claim 6 whereinsaid interleaving means interleaves data encoded by said modulationencoding means in terms of a modulation encoding block as a unit.
 8. Thedata recording apparatus according to claim 4 wherein said modulationencoding means encodes input data in accordance with a trellisconforming to said constraint condition.
 9. The data recording apparatusaccording to claim 8 wherein said interleaving means interleaves dataencoded by said modulation encoding means in terms of a modulationencoding block of said trellis as a unit.
 10. The data recordingapparatus according to claim 1 wherein data is recorded on saidrecording medium in a magnetic, optical or magneto-optical system.
 11. Adata recording method for recording data on a recording medium,comprising the steps of applying predetermined modulation encoding toinput data; and interleaving the modulation-encoded data supplied fromsaid modulation encoding step for re-arraying the data sequence.
 12. Thedata recording method according to claim 11 further comprising:filtering the interleaved modulation-encoded data to compensate forchannel characteristics.
 13. The data recording method according toclaim 11 wherein said input data is error correction coded data.
 14. Thedata recording method according to claim 11 wherein said step ofapplying encodes input data in accordance with a constraint condition.15. The data recording method according to claim 14 wherein said step ofinterleaving interleaves the modulation-encoded data so that saidconstraint condition is satisfied.
 16. The data recording methodaccording to claim 14 wherein said step of applying encodes the inputdata by block modulation.
 17. The data recording method according toclaim 16 wherein said step of interleaving the modulation-encoded datain terms of a modulation encoding block as a unit.
 18. The datarecording method according to claim 14 wherein said step of applyingencodes input data in accordance with a trellis conforming to saidconstraint condition.
 19. The data recording method according to claim18 wherein said step of interleaving interleaves the modulation-encodeddata in terms of a modulation encoding block of said trellis as a unit.20. The data recording method according to claim 11 wherein data isrecorded on said recording medium in a magnetic, optical ormagneto-optical system.
 21. A data reproducing apparatus for reproducingdata recorded by a recording equipment for recording data on a recordingmedium, the recording equipment including modulation encoding means forapplying predetermined modulation encoding to input data and firstinterleaving means for interleaving data supplied from said modulationencoding means for re-arraying the data sequence, said data reproductionapparatus comprising:; deinterleaving means for interleaving reproduceddata in its sequence such as to restore the sequence of data bitsre-arrayed by said first interleaving means to the bit sequence of thedata as encoded by said modulation encoding means; modulation decodingmeans for modulation decoding the data supplied from said deinterleavingmeans; and second interleaving means for interleaving data correspondingto a difference between data output by said modulation decoding meansand data output by said deinterleaving means, based on the sameinterleaving position information as that of said first interleavingmeans, for re-arraying the sequence of the difference data.
 22. The datareproducing apparatus according to claim 21 wherein said modulationdecoding means is fed with a soft input signal and outputs a soft outputsignal.
 23. The data reproducing apparatus according to claim 21 whereinsaid recording equipment includes precode means for filtering datasupplied from said first interleaving means to compensate for channelcharacteristics, and the data reproducing apparatus further comprising:channel decoding means for decoding the channel response.
 24. The datareproducing apparatus according to claim 23 wherein said channeldecoding means is fed with a soft input signal and effects soft outputdecoding.
 25. The data reproducing apparatus according to claim 23wherein said channel decoding means is fed with a soft input signal andeffects soft output decoding based on a trellis corresponding to thechannel response.
 26. The data reproducing apparatus according to claim24 wherein said deinterleaving means interleaves data corresponding todifference between the data output by said channel decoding means anddata output from said second interleaving means; decoding beingiteratively performed between said modulation decoding means and saidchannel decoding means.
 27. The data reproducing apparatus according toclaim 26 wherein said recording equipment includes error correctionencoding means for error correction encoding input data to supply theresulting data to said modulation encoding means, and the datareproducing apparatus further comprising; error correcting soft decodingmeans for soft decoding the error correction code of the soft inputsignal corresponding to soft output data obtained by said modulationdecoding means as a result of iterative decoding.
 28. The datareproducing apparatus according to claim 21 wherein said modulationencoding means encodes the input data in accordance with a constraintcondition; said modulation decoding means effecting decoding conformingto said constraint condition.
 29. The data reproducing apparatusaccording to claim 28 wherein said first interleaving means interleavesdata encoded by said modulation encoding means.
 30. The data reproducingapparatus according to claim 28 wherein said modulation encoding meansencodes the input data by block modulation.
 31. The data reproducingapparatus according to claim 30 wherein said modulation decoding meansincludes likelihood calculating means for calculating the likelihoodvalue corresponding to each output codeword output by said modulationencoding means, wherein the posterior probability information as a softdecision value for an input bit to said modulation encoding means and anoutput bit from said modulation encoding means being calculated usingsaid likelihood value as calculated by said likelihood calculatingmeans.
 32. The data reproducing apparatus according to claim 30 whereinsaid modulation decoding means effects decoding based on a trelliscorresponding to said constraint condition.
 33. The data reproducingapparatus according to claim 30 wherein said first interleaving meansinterleaves data encoded with block modulation by said modulationencoding means in terms of a modulation encoding block as a unit. 34.The data reproducing apparatus according to claim 28 wherein saidmodulation encoding means encodes input data in accordance with saidtrellis conforming to said constraint condition; said modulationdecoding means effecting decoding based on a trellis conforming to saidconstraint condition.
 35. The data reproducing apparatus according toclaim 34 wherein said first interleaving means interleaves data encodedby said modulation encoding means in terms of a modulation encodingblock of said trellis as a unit.
 36. The data reproducing apparatusaccording to claim 22 wherein said modulation decoding means effectssoft output decoding based on the BCJR algorithm or on the SOVAalgorithm.
 37. The data reproducing apparatus according to claim 21wherein data is recorded on said recording medium by a magnetic, opticalor magneto-optical system.
 38. A data reproducing method for reproducingdata recorded by a recording method for recording data on a recordingmedium including a modulation encoding step of applying predeterminedmodulation encoding to input data and a first interleaving step ofinterleaving data encoded in said modulation encoding step, forre-arraying the data sequence, said data reproduction method comprisingthe steps of: deinterleaving the input data in its sequence such as torestore the sequence of data bits re-arrayed by said first interleavingstep to the bit sequence of the data as encoded by said modulationencoding step; modulation decoding the data supplied from said step ofdeinterleaving; and interleaving data corresponding to a differencebetween data decoded in said modulation encoding step and datare-arrayed in said step of deinterleaving, based on the sameinterleaving position information as that of said first interleavingstep, for re-arraying the sequence of the difference data.
 39. The datareproducing method according to claim 38 wherein said step of modulationdecoding is fed with a soft input signal and outputs a soft outputsignal.
 40. The data reproducing method according to claim 38 whereinsaid recording method includes a precode step of filtering data suppliedfrom said first interleaving step to compensate for channelcharacteristics, and the data reproducing method further comprising:channel decoding the channel response.
 41. The data reproducing methodaccording to claim 40 wherein said step of channel decoding is fed witha soft input signal and effects soft output decoding.
 42. The datareproducing method according to claim 40 wherein said step of channeldecoding is fed with a soft input signal and effects soft outputdecoding based on a trellis corresponding to the channel response. 43.The data reproducing method according to claim 41 wherein said step ofdeinterleaving interleaves data corresponding to difference between thedata decoded in said step of channel decoding and data re-arrayed insaid step of interleaving; decoding being iteratively performed betweensaid step of modulation decoding and said step of channel decoding. 44.The data reproducing method according to claim 43 wherein said recordingmethod includes an error correction encoding step of error correctionencoding input data to supply the resulting data to said modulationencoding step, and the data reproducing method further comprising: softdecoding the error correction code of the soft input signalcorresponding to soft output data obtained by said modulation decodingstep as a result of iterative decoding.
 45. The data reproducing methodaccording to claim 38 wherein said modulation encoding step encodes theinput data in accordance with a constraint condition; said step ofmodulation decoding effects decoding conforming to said constraintcondition.
 46. The data reproducing method according to claim 45 whereinsaid first interleaving step interleaves data encoded by said modulationencoding step so that the constraint condition is satisfied.
 47. Thedata reproducing method according to claim 45 wherein said modulationencoding step encodes the input data by block modulation.
 48. The datareproducing method according to claim 47 wherein said step of modulationdecoding includes a likelihood calculating step of calculating thelikelihood value of each output codeword generated and output by saidmodulation encoding step; the posterior probability information as asoft decision value for an input bit to said modulation encoding stepand an output bit from said modulation encoding step being calculatedusing said likelihood value as calculated by said likelihood calculatingstep.
 49. The data reproducing method according to claim 47 wherein saidmodulation decoding step effects decoding based on a trelliscorresponding to said constraint condition.
 50. The data reproducingmethod according to claim 47 wherein said first interleaving stepinterleaves data encoded with block modulation by said modulationencoding step in terms of a modulation encoding block as a unit.
 51. Thedata reproducing method according to claim 45 wherein said modulationencoding step encodes input data in accordance with the trellisconforming to said constraint condition; said step of modulationdecoding effects decoding based on a trellis conforming to saidconstraint condition.
 52. The data reproducing method according to claim51 wherein said first interleaving step interleaves data encoded by saidmodulation encoding step in terms of a modulation encoding block of saidtrellis as a unit.
 53. The data reproducing method according to claim 39wherein said step of modulation decoding effects soft output decodingbased on the BCJR algorithm or on the SOVA algorithm.
 54. The datareproducing method according to claim 38 wherein data is recorded onsaid recording medium by a magnetic, optical or magneto-optical system.55. A data recording and reproducing apparatus for recording andreproducing data for a recording medium, said apparatus comprisingmodulation encoding means for applying predetermined modulation encodingto input data; first interleaving means for interleaving data suppliedfrom said modulation encoding means for re-arraying the data sequence;deinterleaving means for interleaving reproduced data in its sequencesuch as to restore the sequence of data bits re-arrayed by said firstinterleaving means to the bit sequence of the data as encoded by saidmodulation encoding means; modulation decoding means for modulationdecoding the data supplied from said deinterleaving means; and secondinterleaving means for interleaving data corresponding to a differencebetween data output by said modulation decoding means and data output bysaid deinterleaving means, based on the same interleaving positioninformation as that of said first interleaving means, for re-arrayingthe sequence of the difference data.
 56. The data recording andreproducing apparatus according to claim 55 wherein said modulationdecoding means is fed with a soft input signal and outputs a soft outputsignal.
 57. The data recording and reproducing apparatus according toclaim 55, further comprising: precode means for filtering data suppliedfrom said first interleaving means to compensate for channelcharacteristics, and channel decoding means for decoding the channelresponse.
 58. The data recording and reproducing apparatus according toclaim 57 wherein said channel decoding means is fed with a soft inputsignal and effects soft output decoding.
 59. The data recording andreproducing apparatus according to claim 57 wherein said channeldecoding means is fed with a soft input signal and effects soft outputdecoding based on a trellis corresponding to the channel response. 60.The data recording and reproducing apparatus according to claim 58wherein said deinterleaving means interleaves data corresponding todifference between the data output by said channel decoding means anddata output from said second interleaving means; decoding beingiteratively performed between said modulation decoding means and saidchannel decoding means.
 61. The data recording and reproducing apparatusaccording to claim 60, further comprising: error correction encodingmeans for error correction encoding input data, wherein said modulationencoding means modulation encodes data supplied from said errorcorrection encoding means; and error correcting soft decoding means forsoft decoding the error correction code of the soft input signalcorresponding to the soft output data obtained by said modulationdecoding means as a result of iterative decoding.
 62. The data recordingand reproducing apparatus according to claim 55 wherein said modulationencoding means encodes the input data in accordance with a constraintcondition; said modulation decoding means effects decoding conforming tosaid constraint condition.
 63. The data recording and reproducingapparatus according to claim 62 wherein said first interleaving meansinterleaves data encoded by said modulation encoding means.
 64. The datarecording and reproducing apparatus according to claim 62 wherein saidmodulation encoding means encodes the input data by block modulation.65. The data recording and reproducing apparatus according to claim 64wherein said modulation decoding means includes likelihood calculatingmeans for calculating the likelihood value corresponding to each outputcodeword output by said modulation encoding means; the posteriorprobability information as a soft decision value for an input bit tosaid modulation encoding means and an output bit from said modulationencoding means being calculated using said likelihood value ascalculated by said likelihood calculating means.
 66. The data recordingand reproducing apparatus according to claim 64 wherein said modulationdecoding means effects decoding based on a trellis corresponding to saidconstraint condition.
 67. The data recording and reproducing apparatusaccording to claim 64 wherein said first interleaving means interleavesdata encoded with block modulation by said modulation encoding means interms of a modulation encoding block as a unit.
 68. The data recordingand reproducing apparatus according to claim 62 wherein said modulationencoding means encodes input data in accordance with said trellisconforming to said constraint condition; said modulation decoding meanseffects decoding based on a trellis conforming to said constraintcondition.
 69. The data recording and reproducing apparatus according toclaim 68 wherein said first interleaving means interleaves data encodedby said modulation encoding means in terms of a modulation encodingblock of said trellis as a unit.
 70. The data recording and reproducingapparatus according to claim 56 wherein said modulation decoding meanseffects soft output decoding based on the BCJR algorithm or on the SOVAalgorithm.
 71. The data recording and reproducing apparatus according toclaim 55 wherein data is recorded on said recording medium by amagnetic, optical or magneto-optical system.
 72. A data recording andreproducing method for recording and reproducing data for a recordingmedium, said method comprising the steps of: applying predeterminedmodulation encoding to input data; interleaving the modulation-encodeddata for re-arraying the data sequence; deinterleaving reproduced datain its sequence such as to restore the sequence of data bits re-arrayedby said step of interleaving to the bit sequence of themodulation-encoded data; modulation decoding the data supplied from saidstep of deinterleaving; and interleaving data corresponding to adifference between data decoded in said step of modulation decoding anddata re-arrayed in said step of deinterleaving based on the sameinterleaving position information as that of said step of interleavingthe modulation-encoded data.
 73. The data recording and reproducingmethod according to claim 72 wherein said step of modulation decoding isfed with a soft input signal and outputs a soft output signal.
 74. Thedata recording and reproducing method according to claim 72, furthercomprising: filtering data supplied from said step of interleaving themodulation-encoded data to compensate for channel characteristics, andchannel decoding the channel response.
 75. The data recording andreproducing method according to claim 74 wherein said step of channeldecoding is fed with a soft input signal and effects soft outputdecoding.
 76. The data recording and reproducing method according toclaim 74 wherein said step of channel decoding is fed with a soft inputsignal and effects soft output decoding based on a trellis correspondingto the channel response.
 77. The data recording and reproducing methodaccording to claim 76 wherein said step of deinterleaving interleavesdata corresponding to data between the data output by said step ofchannel decoding and data output from said step of interleaving thedifference data; decoding being iteratively performed between said stepof modulation decoding and said step of channel decoding.
 78. The datarecording and reproducing method according to claim 77, furthercomprising: error correction encoding input data, wherein said applyingmodulation encodes data supplied from said step of error correctionencoding; and soft decoding the error correction code of the soft inputsignal corresponding to the soft output data obtained by said step ofmodulation decoding as a result of iterative decoding.
 79. The datarecording and reproducing method according to claim 72 wherein said stepof applying encodes the input data in accordance with a constraintcondition; said step of modulation decoding effects decoding conformingto said constraint condition.
 80. The data recording and reproducingmethod according to claim 79 wherein said step of interleaving themodulation-encoded data interleaves the modulation-encoded data so thatthe constraint condition is satisfied.
 81. The data recording andreproducing method according to claim 79 wherein said step of applyingencodes the input data by block modulation.
 82. The data recording andreproducing method according to claim 81 wherein said modulationdecoding step includes a likelihood calculating step for calculating thelikelihood value corresponding to each output codeword output by saidmodulation encoding step, the posterior probability information as asoft decision value for an input bit to said step of applying and anoutput bit from said step of applying being calculated using saidlikelihood value as calculated by said likelihood calculating step. 83.The data recording and reproducing method according to claim 81 whereinsaid step of modulation decoding effects decoding based on a trelliscorresponding to said constraint condition.
 84. The data recording andreproducing method according to claim 81 wherein said step ofinterleaving the modulation-encoded data interleaves themodulation-encoded data in terms of a modulation encoding block as aunit.
 85. The data recording and reproducing method according to claim79 wherein said step of applying encodes input data in accordance withthe trellis conforming to said constraint condition; said step ofmodulation decoding effects decoding based on a trellis conforming tosaid constraint condition.
 86. The data recording and reproducing methodaccording to claim 85 wherein said step of interleaving themodulation-encoded data interleaves the modulation-encoded data in termsof a modulation encoding block of said trellis as a unit.
 87. The datarecording and reproducing method according to claim 73 wherein saidmodulation decoding step effects soft output decoding based on the BCJRalgorithm or on the SOVA algorithm.
 88. The data recording andreproducing method according to claim 72 wherein data is recorded onsaid recording medium by a magnetic, optical or magneto-optical system.